Background North American studies show bipolar disorder is associated with elevated rates of problem gambling; however, little is known about rates in the different presentations of bipolar illness. Aims To determine the prevalence and distribution of problem gambling in people with bipolar disorder in the UK. Method The Problem Gambling Severity Index was used to measure gambling problems in 635 participants with bipolar disorder. Results Moderate to severe gambling problems were four times higher in people with bipolar disorder than in the general population, and were associated with type 2 disorder (OR = 1.74, P = 0.036), history of suicidal ideation or attempt (OR = 3.44, P = 0.02) and rapid cycling (OR = 2.63, P = 0.008). Conclusions Approximately 1 in 10 patients with bipolar disorder may be at moderate to severe risk of problem gambling, possibly associated with suicidal behaviour and a rapid cycling course. Elevated rates of gambling problems in type 2 disorder highlight the probable significance of modest but unstable mood disturbance in the development and maintenance of such problems.