Aims To determine whether childhood physical abuse (CPA) histories were associated with age of onset of psychoactive substance use and injecting, and the extent of polydrug use among injecting drug users (IDU). Design Cross-sectional. Setting Sydney, Australia. Participants and measurements A total of 300 IDU were administered a structured interview examining the prevalence and severity of CPA and drug use histories. Findings Of the participants, 40.3% had experienced severe abuse (SA), 34.0% mild-moderate abuse (MMA) and 25.7% no abuse history (NA). After controlling for other variables, a history of severe CPA was a significant independent correlate of an earlier age at first alcohol intoxication compared to both the NA (beta = -0.23, P < 0.01) and MMA (beta = 0.20, P < 0.01) groups. Severe CPA was also a significant independent correlate of an earlier age at first illicit drug use compared to both the NA (beta = -0.16, P < 0.05) and MMA (beta = -0.15, P < 0.05) groups. In contrast, CPA histories were not independently associated with the onset of injecting drug use. After controlling for potential confounders, both the MMA (beta = 0.28, P < 0.001) and SA (beta = 0.27, P < 0.001) groups were associated with more extensive life-time polydrug use, but did not differ from each other (P = 0.82). After controlling for potential confounders, both MMA (beta = 0.20, P < 0.01) and SA (beta = 0.33, P < 0.001) group membership were associated with more extensive recent polydrug use but, again, did not differ significantly from each other (P = 0.08). Conclusions Severe childhood physical abuse severity is associated with an earlier initiation into drug use. Any level of abuse is associated with more extensive life-time and recent polydrug use.