Nonfatal heroin overdoses and suicide attempts are both common among heroin addicts, but there is limited knowledge about the association between them. The sample in the present study consisted of 149 regular heroin users in Malmo, Sweden. Out of these 98 had taken an unintentional heroin overdose at some time and 51 had made at least one attempt to commit suicide (but not using heroin). Suicide attempts were significantly more common among those who had taken unintentional overdoses as compared with those who had never taken any overdose (p less than 0.01). The more overdoses, the greater the risk of suicide attempt.