BY DON BOHNING

 In the decade since President George Bush met in Cartagena with the chief
 executives of Colombia, Peru and Bolivia, Colombia has emerged as the dominant
 country in virtually all aspects of the drug trade.

 ``We depart Cartagena having forged an unprecedented alliance against the drug
 trade . . . the first anti-drug cartel,'' Bush said on leaving the Colombian coastal
 city on Feb. 15, 1990, after a four-hour summit. That was the last presidential visit
 to Colombia prior to Wednesday.

 The most notable difference since 1990, according to U.S. anti-drug fighters, is
 the centralization of production, processing and distribution in Colombia. That was
 not the case in 1990 when Bolivia and Peru were the main producers of coca, the
 raw material for cocaine.

 As recently as 1995, the amount of coca produced in Peru and Bolivia combined
 would result in the production of 700 metric tons of cocaine while coca produced
 in Colombia would account for only 230 tons.

 By 1999, according to the White House Office on National Drug Control Policy,
 that number for Bolivia and Peru had dropped to 145 metric tons and for Colombia
 had soared to 520 metric tons. Coca cultivation declined by 66 percent in Peru
 and 55 percent in Bolivia during the same period.

 When Bush visited Colombia, the country was producing virtually no heroin.

 Now, it is estimated that 90 percent of the cocaine entering the United States and
 70 percent of the heroin seized here comes from Colombia, according to Robert
 Weiner of the White House Office of National Drug Control Policy.

 Back then, also, Colombia's violent Medellin Cartel, ruling by terror and
 intimidation, controlled virtually all aspects of the drug trade; then came the
 white-collar Cali Cartel with its computers, accountants and lawyers, designed to
 beat the system.

 Now, say U.S. law enforcement officials familiar with the drug trade, drug
 organizations have learned from the mistakes of the past and specialize in single
 aspects of the business such as production, processing, transportation,
 distribution and money laundering instead of controlling the entire operation.

 ``Everybody's got a piece of the pie now. The organizations are a lot smaller and
 every one is developing its own expertise,'' said one official.

 Still, U.S. officials say drug demand has dropped significantly in the United
 States, while Europe has become an increasingly attractive market, because of
 the higher prices the product commands there.

 ``There are new markets in Europe because that's where the money is,'' said one
 official. ``This is a business driven by greed.''