Certainly towards the end of his life Crowley was a heroin addict. He took large daily injections, as much as his doctor would prescribe, it seems. He did take heroin as a cure for asthma. His most fervent admirers like to make excuses for him, but the fact remains.
Kenneth Grant, one of his more enthusiastic 'followers' recalls in Remembering Aleister Crowley:
[FONT=Arial,Helvetica]"The complications which Crowley found too fearful to contemplate concerned his need for medicaments which he was taking against his severe bouts of asthma. His health was deteriorating rapidly and when I finally went to stay with him many of my services consisted in getting doctors and chemists to supply substances which they were far from eager to dispense. These included veronal, heroin, ethyl oxide, and cocaine. The state of Crowley's health necessitated such massive doses that one doctor in Hastings hinted to me in confidence that he feared that his patient was a drug addict! Nevertheless, despite his poor physical condition, Crowley never lost his mental elasticity and alertness."