OBJECTIVES: To evaluate the clinical and cost-effectiveness of quetiapine, olanzapine and valproate semisodium in the treatment of mania associated with bipolar disorder. DATA SOURCES: Electronic databases; industry submissions made to the National Institute for Clinical Excellence. REVIEW METHODS: Randomised trials and economic evaluations that evaluated the effectiveness of quetiapine, olanzapine or valproate semisodium in the treatment of mania associated with bipolar disorder were selected for inclusion. Data were extracted by one reviewer into a Microsoft Access database and checked for quality and accuracy by a second. The quality of the cost-effectiveness studies was assessed using a checklist updated from that developed by Drummond and colleagues. Relative risk and mean difference data were presented as Forest plots but only pooled where this made sense clinically and statistically. Studies were grouped by drug and, within each drug, by comparator used. Chi-squared tests of heterogeneity were performed for the outcomes if pooling was indicated. A probabilistic model was developed to estimate costs from the perspective of the NHS, and health outcomes in terms of response rate, based on an improvement of at least 50% in a patient's baseline manic symptoms derived from an interview-based mania assessment scale. The model evaluated the cost-effectiveness of the alternative drugs when used as part of treatment for the acute manic episode only. RESULTS: Eighteen randomised trials met the inclusion criteria. Aspects of three of the quetiapine studies were commercial-in-confidence. The quality of the included trials was limited and overall, key methodological criteria were not met in most trials. Quetiapine, olanzapine and valproate semisodium appear superior to placebo in reducing manic symptoms, but may cause side-effects. There appears to be little difference between these treatments and lithium in terms of effectiveness, but quetiapine is associated with somnolence and weight gain, whereas lithium is associated with tremor. Olanzapine as adjunct therapy to mood stabilisers may be more effective than placebo in reducing mania and improving global health, but it is associated with more dry mouth, somnolence, weight gain, increased appetite, tremor and speech disorder. There was little difference between these treatments and haloperidol in reducing mania, but haloperidol was associated with more extrapyramidal side-effects and negative implications for health-related quality of life. Intramuscular olanzapine and lorazepam were equally effective and safe in one very short (24 hour) trial. Valproate semisodium and carbamazepine were equally effective and safe in one small trial in children. Olanzapine may be more effective than valproate semisodium in reducing mania, but was associated with more dry mouth, increased appetite, oedema, somnolence, speech disorder, Parkinson-like symptoms and weight gain. Valproate semisodium was associated with more nausea than olanzapine. The results from the base-case analysis demonstrate that choice of optimal strategy is dependent on the maximum that the health service is prepared to pay per additional responder. For a figure of less than 7179 British pounds per additional responder, haloperidol is the optimal decision; for a spend in excess of this, it would be olanzapine. Under the most favourable scenario in relation to the costs of responders and non-responders beyond the 3-week period considered in the base-case analysis, the incremental cost-effectiveness ratio of olanzapine is reduced to 1236 British pounds. CONCLUSIONS: In comparison with placebo, quetiapine, olanzapine and valproate semisodium appear superior in reducing manic symptoms, but all drugs are associated with adverse events. In comparison with lithium, no significant differences were found between the three drugs in terms of effectiveness, and all were associated with adverse events. Several limitations of the cost-effectiveness analysis exist, which inevitably means that the results should be treated with some caution. There remains a need for well-conducted, randomised, double-blind head-to-head comparisons of drugs used in the treatment of mania associated with bipolar disorder and their cost-effectiveness. Participant demographic, diagnostic characteristics, the treatment of mania in children, the use of adjunctive therapy and long-term safety issues in the elderly population, and acute and long-term treatment are also subjects for further study.