This article is a systematic review of drug treatments for disordered and problem gambling. The authors found 17 randomised clinical trials comparing a drug treatment to placebo or another category of drug treatment. The review provides some support for the use of opioid antagonists and atypical antipsychotics (olanzapine) in decreasing gambling symptoms in the short term. There is a lack of evidence on whether these drugs can improve gambling behaviours or psychosocial functioning. There is no evidence to support the use of antidepressants. The effects of mood stabilisers (including anticonvulsants) are unclear. The certainty of the evidence regarding any drug treatment is low or very low. Therefore, the findings should be interpreted with caution.