There are about 35 million handicapped persons in the United States, perhaps 19 million of them with some sort of mobility impairment, and they are traveling in growing numbers and becoming increasingly militant about demanding rights and travel opportunities equivalent to those available to the able-bodied.

One of the groups lobbying for a better deal for the handicapped traveler is The Society for the Advancement of Travel for Handicapped (SATH), a Brooklyn-based organization with some 300 members in 18 countries. SATH advocates and promotes travel for the disabled through its bimonthly newsletter and annual seminars, usually held outside the country. i

SATH is nonprofit but its membership includes representative of commercial travel agencies specializing in, or at least offering, tours geared to the handicapped. A list of these agencies can be obtained by writing to: Society for the Advancement of Travel for the Handicapped, 26 Court St., New York, N.Y. 11242.

"Things are getting a lot better for the handicapped," said Richard Dresser, an employe of the Information Center for Individuals with disabilities in Boston. "I have an electric wheelchair and airlines will not transport regular wet-cell batteries, but now there is a new type of non-spill battery that can be carried. . . having an electric wheelchair with you means that you are so much more independent."

For more than a decade, the basic guidebook for wheelchair travelers has been "The Wheelchair Traveler" by Douglas R. Annand, a former Marine Corps pilot who lost the use of his legs in a plane crash and has been in a wheelchair for 28 years.

Annand, who personally researches most of the guide, list more than 6,000 hotels, motels, and restaurants in the United States, Canada, Mexico and Puerto Rico, rated on their suitability for the handicapped. All have at least a 26-inch-wide door opening, for example. Annand's guide is priced at $7.95 and can be ordered from: The Wheelchair Traveler, Ball Hill Road, Milford, N.H. 03055. Delivery takes about two weeks.

Many airlines now publish consumer guides for the handicapped, explaining any restrictions on travel by the disabled -- unaccompanied wheelchair travelers sometimes have to produce medical confirmation of their ability to fly alone, for instance -- and detailing services such as pre-boarding and special meals for passengers with dietary requirements.

The U.S. government publishes a 20-page guide called "Access Travel" which gives design features, facilities, and services for the disabled at 220 airport terminals worldwide. It is available free from the General Services Administration Consumer Information Center, Washington, D.C. 20405.

The federal government gives high priority to expanding facilities for the handicapped, incorporating them ino all new construction and insisting that they be a part of any building or project involving substantial federal funding. AMTRAK, for example, not only has wheelchair-accessible toilets but also bedrooms designed especially for the handicapped in its new long-distance bi-level cars.

Access guides to their facilities are available from the U.S. Park service, the Smithsonian Institution, and other governmental agencies, both state and federal. A useful 24-page International Directory of Access Guides -- which list virtually all of them -- is available free from Rehabilitation International USA (RUUSA), 20 West 40th St., New York, N.Y. 10018.

The best general travel guide for the handicapped, and the first of its kind, is: "Access to the World" by Louise Weiss, Chatham Square Press, 178 pp., $7.95. It covers air, bus, rail, ship and auto travel; includes data on destinations, access guides, hotels and motels, travel agents and tour operators, health and medical problems, and provides useful travel tips for the disabled.

"The handicapped want to work and play like everyone else," said Weiss, "and they manage to do so despite architectural barriers that keep them out of buildings and transportation facilities, as well as mental barriers that make them almost invisible to the able-bodied population."