This paper provides a mainly qualitative investigation of the role of methadone and methadone treatment in non-fatal illicit drug overdose. During 1997 and 1998, semi-structured interviews were conducted with 33 individuals in six hospital accident and emergency departments in two Scottish cities. The research identified four overdose situations related to methadone/methadone treatment. These were: (1) topping up a legitimate methadone prescription; (2) abusing another's methadone prescription; (3) preferring illegal drugs to prescribed methadone; and (4) failing to obtain prescribed methadone. The implications of these findings for methadone treatment policy and practice are discussed.