Circulating thiamine, riboflavin, nicotinates, folates, vitamin B12, B6, A, and carotenes of 149 heroin addicts aged 17-60 years were compared to 204 healthy subjects not using drugs or vitamins. Only 24 per cent of the addicts had no evidence of hypovitaminemia; 45 per cent and 37 per cent had vitamin B6 and folate deficit respectively, whereas deficits of thiamine, vitamin B12, riboflavin, and nicotinate were recorded for 13-19 per cent of the addict population; impaired liver function in addicts did not influence these results.