Many methadone patients and untreated heroin users have an ambivalent attitude toward methadone maintenance. This may be a result of the widespread belief that methadone produces various side effects not found with heroin. This study compared the symptom complaints of patients on oral methadone maintenance (MMT) with those of patients prescribed injectable heroin (IHT). A convenience sample of 117 (63 MMT, 54 IHT) patients was recruited from two maintenance clinics. With the use of a self-completion questionnaire, patients were interviewed about a range of symptoms they had experienced and which, in their view, were due to maintenance substance immediately after the last 10 opioid administrations, during the previous week and previous year. The complaints of the two groups overlapped considerably with only few significant differences; these appeared related to the route of administration. IHT patients reported a larger number of complications experienced immediately after administration than MMT patients (p = .007). From the patients' view, methadone does not produce many more or side effects very different from heroin and thus seems at least as tolerable as heroin for maintenance treatment.