This pilot trial explored the effectiveness of an adjunctive single session of motivational interviewing (MI) to reduce crack cocaine use in a methadone maintenance treatment population. Twenty-nine participants were cluster randomised by clinician to MI or a crack information control condition as part of treatment as usual. The intervention had a modest impact on one crack cocaine measure but was not statistically significant in this small sample. A large and statistically significant reduction in heroin use amongst those in the MI condition was observed. This pilot study demonstrated that it was feasible to incorporate a psychosocial intervention within a busy outpatient methadone maintenance programme and the findings support the value of undertaking a larger trial.