MILLIONS OF AMERICANS travel overseas annually, some for business and some for pleasure. Estimates are that one out of every four experience some type of medical emergency while away from home. In the case of major illness, returning home on a stretcher can cost a few thousand dollars and can present staggering problems, particularly if a traveler is alone and stricken in a remote area.

While some types of travel insurance do cover medical charges abroad, most do not pay for the high costs of emergency transportation. Travelers who need to return home with special medical provisions, such as a stretcher, can be faced with paying the equivalent of four first-class air fares -- if commercial airline service is available and if the airline will agree to handle the patient.

In areas served by no commercial carrier, chartered air ambulance service (which can provide vital monitoring equipment) is even more expensive, costing from $3,000 to $7,000.

To the rescue have come three companies which are now offering programs to help travelers meet these expenses. Two, NEAR (Nationwide/Worldwide Emergency Ambulance Return, Inc.) and HOME (Help in Overseas Medical Emergencies), are newcomers. The third, international SOS Assistance Inc., began offering services in 1966 in Europe and in 1976 in the United States.

Each company offers a program whereby members are entitled to financial and/or medical assistance for an annual fee. NEAR and HOME, which are geared more to the individual traveler and charge from $12 to $42, will cover all costs in transporting a disabled member. SOS, which has catered primarily to corporate clients, bills the company for the actual transportation costs incurred.

In addition to emergency transportation service, most of the programs include various benefits such as a 24-hour, toll-free emergency phone number, an international message center, a lost-and-found service, coverage of transportation costs for dependents to return home and for a family member to join the disabled, and access to a worldwide network of doctors and medical centers. While each program does emphasize different emergency services, they all seek to aid the traveler as quickly and efficiently as possible after a disaster or emergency strikes.

Both SOS and HOME specify that members will be evacuated either "to the nearest suitable hospital" (HOME) or "nearest facility capable of providing required care" (SOS). They do not guarantee evacuation home in every case. In contrast, NEAR does specify that the member will be returned "home" where the member lives. Yet it is important to note that, in all cases, there is no automatic right to evacuation -- medical approval must be given as outlined in the provisions of the individual programs.

International SOS assistance chairman Claude Giroux founded his service after needing emergency assistance himself while on vacation in Sardinia.

A fire engulfed his campsite, his youngest child was badly burned and many personal possessions were destroyed, including identification papers and money. "There I was," he recalled, "with all the insurance in the world and plenty of money at home. Yet I was helpless."

With headquarters in Geneva and Philadelphia, SOS provides members and organizations with a number of services for fees ranging from $10 for one to seven days of travel to $120 for a year's agreement.

"We have about 4,000 doctors on retainer to us," explained Richard Searle, a sales manager. "They are on call and ready to provide emergency medical care, backstopped by a fleet of medically equipped aircraft or helicopters. We own parts of leasing companies and have about 200 aircraft available to us," he said.

In addition to these services, SOS also provides telephone access to a worldwide, monitored, multilingual network of medical centers; personal medical profile booklets; emergency hospital deposits; transportation for families to join disabled members, and return of unattended member children.

The program is underwritten by Lloyd's of London and Union Swiss.

The main difference, however, between SOS and both NEAR and HOME is that SOS members or their employers must eventually pay the cost of medical services and evacuations. The program mainly provides easy access to such services, which is why it bills itself as "a most vital supplement to your insurance coverage," and not as an insurance program.

This difference explains why it is very popular with corporations. Searle said approximately 100 corporations subscribe to the service, "most of them being large, multinational firms who station a large number of employes overseas." Recent corporate clients include Exxon, Rockwell, GTE, General Motors, Union Carbide and General Electric.

Dr. Gene Moore, who handles the program for Exxon, said the primary reason they chose SOS was "because it offered the best communication system, conscientious service and a strong base in Europe."

"We've had three evacuations with them and we were very pleased with the service," Moore remarked. His company pays an annual membership of $1,800 for the service. Exxon, he said, employs about 120,000 people, most of whom work abroad.

While SOS has concentrated its marketing more on the corporate side, said Searle, in the past six to eight months the company has been "reaching out to the general public . . . We got a lot of mileage out of our work with the U.S. team and five other teams at the 1980 Winter Olympics. We served as the official backup medical security."

Searle also said the company has been involved in disaster coordination efforts and recently helped transport victims from a bus crash in Mexico in which 16 were injured and eight killed.

Information and applications are available from International SOS Assistance, Inc., Walnut St., Philadelphia, Pa. 19102, 215-732-9091.

Concentrating more on the individual traveler, NEAR began offering single and family memberships only six months ago. "People kid themselves that it's always the other guy and never you," said NEAR president Joe Travis, an Oklahoma oil man who decided to come to the rescue of the "other guys."

After all, he said, "about 23 million Americans traveled overseas in 1978, for example, and of that number 10,000 died while abroad and several hundred thousand either became seriously ill or were hospitalized."

Underwritten by Lloyd's of London, the membership program has yet to advertise. Just from a few newspaper articles, calls and letters have been pouring into the company's Oklahoma headquarters. "We have been deluged with inquiries from across the country," Travis said. "We have even received calls from overseas residents who ask if they are eligible."

Several newspapers ran stories about NEAR along with a widely distributed article by Dr. Gregory R. DeVore, whose father suffered a heart attack while vacationing in French Polynesia.

The trauma endured by his family resulted from lack of communication about how and when to transport his father home. Commercial carriers said they "would not be able to transport my father until six weeks had passed," wrote Dr. DeVore. The Defense Department told him a med-evac plane would cost $2,000, then $6,000 to 10,400 and finally $72,000 -- which had to be paid in full before evacuation. When asked what if people did not have the money, an official responded, "then they would die."

Eventually the doctor was able to fly his father home on a commercial carrier, but the total cost of the emergency was $17,000.

For $42 a year, NEAR provides an entire family with free air and ground transportation home from anywhere in the world in event of illness, accident or death. "Each member," explained Travis, "receives a card with our toll-free number and a telex number on it. Just a call can set our wheels in motion.For medical evacuations, we will either make the reservations for a commercial flight or charter an air ambulance. We will provide payment through a letter of credit or reimburse the traveler when he returns."

NEAR will work closely with the attending physician to determine if evacuation is necessary. "Two doctors, one an international diplomat and the other a state official, serve on our board of directors and they will determine, along with the attending doctors, a traveler's situation," said Travis.

NEAR also offers an international 24-hour message service, a lost-and-found service which forwards items to the next destination and free emergency contact service to members of the immediate family.

Applications are available from NEAR, Inc., 1900 N. MacArthur, Suite 210, Oklahoma, City Okla. 73127. Phone (toll-free) 800-654-6700.

The third program, which began only weeks ago, is called HOME. Offered by the International Travelers Association, a nonprofit mutual benefit company, HOME is available only to American citizens and provides coverage only outside the United States.

"While the State Department assistas whenever possible," said Gary Johnson, a HOME spokesman, "it cannot provide funds for the high costs needed in most medical emergencies. We encourage the traveler to contact the local embassy or consulate and then we can arrange funding and provide whatever services are necessary."

For $12 a year, HOME offers five major services: medical evacuation, deceased repatriation, foreign burial if requested, return of minors to their U.S. homes and all physician services necessary in the diagnosis and treatment of an illness prior to evacuation.

"HOME is not meant to take the place of a comprehensive health plan for people who travel," noted President Stephen Dobrenchuk. But, he added, he does hope it becomes "a travel option considered a necessity by the vast majority of international businessmen and excursionists."

Dobrenchuk said he saw the need for the program while handling overseas emergencies for the State Department. After leaving the department, he began investigating ways of "offering prompt financial assistance to Americans in the event of an emergency abroad since the consular office cannot come up with the money," he said. "Especially in the case of death, no one will return the body to the States just like that. Frequently, families have to scramble to send money as soon as possible for removal of the body."

Since government funds were not available, he turned to the private sector for backing. He met with officials of a European country that offers an emergency travel program for its citizens and then consulted a Lloyd's of London agent before establishing the membership organization. He also hooked up with Medex International, a worldwide physician and hospital service, and a British firm that handles evacuations worldwide.

Dobrenchuk explained how HOME would handle an emergency:

"The traveler would contact the embassy or consulate informing them of the problem. If an evacuation is recommeded by the attending physician, the embassy or the member would place a call to Medex, whose staffers will then make the necessary arrangements. Financial assistance will be proptly channeled through the State Department to the embassy or consulate."

The only exclusions involved medical service in noncritical conditions, suicide, flying in nonregulated aircraft and war."

For further information or applications from HOME, write to the International Travelers Associations, 1100 17th St. NW, Washington, D.C. 20036.

While Dobrenchuk said no mishaps have occurred to members yet, he pointed out that "these things do happen. No one wants to think of the worst, but travelers should always ask, What if?'"

HOME, NEAR and International SosY Assistance are trying to answer that question for travelers worldwide.