KABUL, Afghanistan  The men, hollow-eyed and matted, start coming at dawn, shuffling into the remains of the old Soviet Cultural Center, which in its day staged films celebrating the glories of a new era.

These days, the shell of the abandoned building serves as perhaps the world’s largest gathering spot for men looking to satisfy their lust for heroin and opium. Stooping in the darkened caverns of the place, amid the waste and exhalations of hundreds of others, the men partake of the drug that has begun to wreak its deathly magic in the very country where it is produced.

One such man, who called himself Mohammed Ofzal, struck a match beneath a piece of foil and sucked in the blue smoke that rose from the liquefying little mass. Then he sat back in a crouch, legs shaking a little. His eyes, glazed and half-shut, stared blankly at the floor.

“My parents are fed up with me; they are telling me to quit,” Mr. Ofzal said. He said he was 18. His clothes, unlike nearly everyone else’s in the gathering post, were pressed and clean. He said he would go home soon; he would not be spending the night. “If you don’t take care of yourself, you could die here.”