Aims. To examine the relationship between attempted suicide and non‐fatal heroin overdose among methadone maintenance patients. 
Design. Cross‐sectional survey. 
Setting. Sydney, Australia. 
Participants. Two hundred and twenty‐three methadone maintenance patients. 
Findings. Forty per cent of participants reported a history of at least one suicide attempt. Females were significantly more likely than males to have attempted suicide (50% vs. 31%), and to have done so on more than one occasion (28% vs. 15%). There was a large difference between males and females in the onset of attempted suicide. Females reported an initial attempt, on average, 6 years earlier than males (18.3 vs. 24.7 years), and were significantly more likely than males to have attempted suicide prior to the onset of heroin use (69% vs. 11%). While heroin overdose was common among the sample (66%), the most common methods employed for suicide attempts were overdose of a non‐opioid drug (21%) and slitting of wrists (20%). A deliberate heroin overdose as a means of attempted suicide was reported by 10% of participants. Heroin overdoses appeared overwhelmingly to be accidental. Ninety‐two per cent of those who had overdosed reported that their most recent overdose was accidental. 
Conclusions. Attempted suicide presents a major clinical problem to staff at drug treatment programmes, but one distinct from heroin overdose. While both overdose and suicide present increasing clinical problems, they are separate problems, and require different responses.