Paying about $2 million, Juan Ramon Matta Ballesteros bribed 18 prison guards and walked to freedom through seven doors of a Bogota prison in March. Accused of narcotics trafficking in the United States, and wanted as well in Mexico for the murder last year of a U.S. narcotics agent, Matta Ballesteros had been the most important accused drug dealer that Colombia had managed to put behind bars.

His escape to Honduras -- his native country and one that does not permit the extradition of its nationals -- set back Colombia's antidrug effort and triggered the resignation of the director of prisons.

The Matta Ballesteros episode underscored what Colombian authorities are up against as other major traffickers continue to evade the law's grip here by using bribes, intimidation, cunning or assassination.

Nevertheless, Colombia receives high marks from U.S. officials for at least making a dent in the country's multi-billion dollar narcotics business. The Reagan administration is looking forward to continued cooperation on the drug front from Colombian President-elect Virgilio Barco Vargas, who takes office in August.

Barco, a civil engineer with a long career in public service, has a Calvinist streak that aides say will ensure he does not bring those tainted by the drug trade into his government. His service overseas as ambassador to London and Washington and as a World Bank director has made Barco sensitive to Colombia's international image, which a senior adviser said the new president wants to cleanse.

Yet Barco has said little publicly about what he intends to do about narcotics. The problem was not even listed on his Liberal Party's platform, nor was it raised by other candidates during the campaign.

This absence of public debate did not surprise Colombians. It reflected the low priority that people give the drug issue in public opinion surveys that rank social and economic concerns.

Narcotics are still generally viewed as more a U.S. than a Colombian problem. That perception persists despite reports, like a front-page article Saturday in Bogota's El Espectador, that 3 million of Colombia's 28 million people are drug addicts.

Some Colombians resent U.S. efforts to curtail a business that means money and jobs for the Colombian economy and that is perceived as being allowed to prosper in the United States. A recent television documentary, for instance, contended that while the United States was pressing for the eradication of marijuana plants in Colombia, its own marijuana harvest last year was the biggest in American history.

"To this day, the general public, and even some Colombian politicians, are not all that well informed about the problem," said a U.S. official involved in combating narcotics. "Many still hold notions that the druggers have promoted and that play on nationalist sentiment."

Only after the April 1984 murder of justice minister Rodrigo Lara Bonilla by two gunmen believed to have been hired by traffickers did President Belisario Betancur declare war on the narcotics trade -- dropping his earlier reluctance to extradite Colombians wanted on U.S. drug charges.

In the two years since, Colombian authorities have demonstrated a willingness to cooperate with U.S. narcotics agents that American officials say is unmatched in Latin America.

According to U.S. estimates, aerial spraying has eradicated 85 percent of Colombia's marijuana, which once sprouted on the slopes of the northern mountains.

Colombians, however, have turned to wholesale production of cocaine, a much more lucrative drug. Limited spraying against coca plants growing in eastern and southern jungle regions started this year.

The heart, though, of Colombia's drug industry is not in cultivating coca plants but in refining into white powder the cocaine paste brought from Bolivia and Peru.

A 1,500-person antinarcotics police unit, equipped with about 30 aircraft and assisted by the military, has raided jungle airfields and cocaine processing laboratories. Last year, 90 airstrips and 667 labs were hit, more than double the strikes in 1984.

One of the first tasks that Barco faces -- and one that U.S. officials will be watching closely -- is finding a replacement for retiring national Police Chief Gen. Victor Delgado Mallarino, credited with spearheading the antidrug campaign.

U.S. figures show that the amount of cocaine captured in 1985 was actually much less than in 1984 -- 9,500 metric tons compared to 21,300. A Drug Enforcement Administration (DEA) agent said the decrease is because the 1984 figure was exceptionally high as a result of a raid on an enormous compound of lab facilities in early 1984. The agent also said that the statistics do not show the tons of cocaine seized outside Colombia on the basis of intelligence provided by Colombian police.

U.S. officials say the antinarcotics drive has been hindered lately by a truce between the government and Colombia's largest guerrilla movement, the Revolutionary Armed Forces of Colombia, or FARC. Although FARC spokesmen deny their group is involved in the drug trade, police say the guerrillas provide security at remote clandestine airstrips and processing laboratories and carry out assassinations and extortion for traffickers. In exchange, FARC reportedly receives arms, ammunition and money.

But because senior government authorities are reluctant to engage the FARC in combat in view of the truce, antidrug raids in areas where the guerrillas operate require a long approval process.

Renewed fighting between the military and those guerrilla movements which last year renounced cease-fire agreements has also interfered with the antinarcotics campaign by sapping the resources of the armed forces, according to police agents.

The Colombian government has arrested one-third of the fugitives sought by the United States under a 1982 extradition treaty. Twelve Colombians have been extradited to the United States, and two U.S. citizens wanted here on drug charges were extradited to Colombia.

The first American delivered was John L. Tamboer, handed over in June 1985. He emerged from prison in late May on a bail of $100,000 after a Bogota judge ruled that procedural errors had been committed in his case.

Colombian police forces collaborated in the past year with Ecuador on their first cross-border eradication project. They also gave tactical and logistical support to the first coca interdiction drive launched by Peruvian President Alan Garcia. In April, in a demonstration of regional cooperation applauded by the United States, Bolivia, Colombia, Ecuador, Peru and Venezuela signed a pact to combat the cocaine trade.

In fiscal 1986, U.S. anti-drug assistance grants to Colombia's national police and regional interdiction projects total $14.7 million.

Colombia remains the source of about 80 percent of the world's cocaine, according to DEA estimates, and accused drug barons are still at large.

But in an indication that Colombia's crackdown is having some impact, leading traffickers tried last month to negotiate a deal with the government. In an open letter to the Colombian press dated May 6 and claiming to represent 65 narcotics traffickers -- some in jail awaiting extradition, others in hiding -- the drug makers offered to finance Colombia's $13.5 billion external debt, transfer funds from foreign banks back to Colombia, and surrender their processing laboratories, all in return for a guarantee they would be prosecuted in Colombia, expecting more lenient treatment at home.

U.S. and Colombian officials interpreted the letter as both an attempt to entice the outgoing Betancur administration into a last-minute arrangement and an early gesture to the incoming Barco government.

Justice Minister Enrique Parejo Gonzalez termed the petiton "absurd and illegal" and said the only dialogue the traffickers could have with authorities would be with judges.

Colombian traffickers made a similar bid in late 1984, meeting in Mexico city with ex-president Alfonso Lopez Michelsen, then later in Panama city with prosecutor general Carlos Jimenez Gomez. The government never accepted their offers.