First, some quotes from two DEA agents with direct first-hand experience:
 

It's only fair to expect a newcomer to these sordid affairs to be skeptical about conspiracy theories of widespread and deliberate government involvement in drug running. After all, one reasons, Would the U.S. Government or the CIA deliberately poison its own citizens or destabilize its own society? 

"Here's my problem. I think that if people in the government of the United States make a secret decision to sacrifice some portion of the American population in the form of ... deliberately exposing them to drugs, that is a terrible decision that should never be made in secret." (- Jack Blum, speaking before the October 1996 Senate Select Intelligence Committee on alleged CIA drug trafficking to fund Nicaraguan Contras in the 1980s, Chaired by Senator Arlen Specter).

In all honesty, the answer to the above question depends on which 'CIA' you are referring to. There are many factions in the U.S. intelligence community, some 'privatized' and unofficial, some grotesquely Machiavellian (including the nearly 1,000 foreign CIA agents removed from the CIA's payroll in 1997, for their known human rights and criminal abuses!). The various factions of the U.S. Intelligence community are inter-networked in various capacities to continue and further U.S. foriegn policy objectives. The CIA is the heart of this immense system. 
 

"For criminal organizations, participating in covert operations offers much more than money. They may get a voice in selecting the new government. They may get a government that owes them for help in coming to power.They may be able to use their connections with the United States government to enhance their political power at home and towave off the efforts of the American law enforcement community." (Prepared October 1996 statement of Jack Blum (former special counsel to the 1987 "Kerry" Senate Foreign Relations Subcommittee on Terrorism, Narcotics and International Operations) for the October 1996 Senate Select Intelligence Committee on alleged CIA drug trafficking to fund Nicaraguan Contras in the 1980s, Chaired by Senator Arlen Specter)

Oversimplified, the CIA's primary global foreign policy method is to gain influence and control by whatever means necessary. To be a bit more clear, let's compare civilian police against covert operatives. In police work, law enforcement dealings with underworld elements are always difficult and wraught with ethical problems, but civilian police are subject to rules and oversight. Conversely, the CIA is comparatively unencumbered by the rules that govern civilian police corps, and suffers little Congressional oversight. The result of this extreme freedom in executing policy, is that the CIA's official and unofficial operatives involved in its covert operations division are free to pursue military objectives with whatever means they see fit. 

These operatives are covert warriors, they are key in expanding the US sphere of influence. In order for covert actions to be effective politically and militarily, the CIA employs parts of the underworld as its operatives (like the thousand foreign agents mentioned above). After all, who knows the political and social terrain better than the local mob? But, once employed by the CIA, these criminal enterprises naturally expect some kind of quid-pro-quo, and in order to concentrate power via its foriegn underworld proxies, the CIA has to find ways to reward and empower its criminal proxies. If the CIA really wants to gain influence and control in countries and economies via alliances with underground criminal enterprises, and if these alliances entail protecting drug piplines, well, the end justifies the means. 

After all, building an empire is a nasty business, and if the choice is overt action (war) or covert action (conspiracy), the latter is preferred. Taking an even more Machiavellian view, you suffer collateral losses either way, either in the form of wartime casualties or drug war casualties (which some argue offers the state additional advantages of divide-and-conquer propaganda and an increased police state). 

The CIA euphemistically terms this "radical pragmatism," which, in the case of drugs, has come to mean protecting narcotics pipelines. The functional upshot of this is that narco-colonialism is alive and well and is residing centrally at CIA headquarters in Langley, VA. 

There is a veritable mountain of documented and eye-witness evidence spanning nearly the four post-war decades of the Cold War. This history begins with the CIA's predessor, the OSS, freeing mafia don Lucky Luciano from a New York prison to assist them in suppressing leftist unions in Italy; however, the OSS also protected Luciano's heroin trafficking (as a matter of record, some congressmen created this document). 

To avert the risk of loosing focus, this site concentrates on the modern era which begins with the CIA's covert war in Laos, emphasizing the Latin American cocaine wars of the 1980's & '90's. Tying it all together, this narrative attempts to bring to light, to anyone willing to spend a few hours of their time, one of the most disturbing facets of the Cold War and post-Cold War eras. 

One last disclaimer before proceeding: What won't be found here are wild 'secret agent man' stories that sound too good to be true. Many of these kind of accounts have been either found uncorroborable or so full of inconsistencies that the information is generally useless and misleading. Same goes for testimonials from 'reformed' drug runners (who almost invariably have legal problems stemming from their alleged drug running for the government) and 'former' spooks (whose stories are so odd as to make them immediately suspect as whether they are in fact an active spook disseminating disinformation).