It is commonly agreed in law enforcement that Afghanistan has produced anywhere from 70 to 80 percent of the world's opium supply for at least the last decade. E.g., "Afghanistan produced over 70 percent of the world's supply of illicit opium in 2000." -- Asa Hutchinson Administrator, Drug Enforcement Administration, October 3, 2001.
In addition, it has been repeatedly documented that Pakistan's Inter-Services Intelligence has been involved in the processing and trafficking side of the equation since the late-1980's. More recently - and under pressure from organizations such as the UN Drug Control Program - the Pakistani heroin labs have been shut down, and simply moved across the border into Afghanistan. A simple shell game. Again from Hutchinson, "In the past, many opium processing laboratories were located in Pakistan, particularly in the Northwest Frontier Province (NWFP). These laboratories appear to have relocated to Afghanistan, both to be closer to the source of opium and to avoid law enforcement actions by the Government of Pakistan."
Actually, you might want to read all of Hutchinson's comments, since he does a reasonably good job of summarizing the relationship between bin Laden, the Taliban, and opium/heroin distribution.
Unfortunately Pakistani involvement has been downplayed to some extent for the last several years, and there's little discussion of the degree to which bin Laden secured heroin deals with the Russian Mafiya. But still a worthwhile read.
Even cursory research makes it clear that al Qaeda and bin Laden are financing their activities through 70 to 80 percent of the world's wholesale opiate traffic (depending upon whose numbers you use).