The aim of this study is to clarify the potential benefits, disbenefits and costs of Orlistat for the treatment of obesity. The method was a search for relevant systematic reviews and randomized controlled trials, in Medline, Pre-Medline, Embase and the Cochrane Library, using Orlistat and its synonyms. Identified trials were appraised using a standard appraisal checklist and trial data were extracted for use in cost-effectiveness modelling. Three large multicentre, randomized placebo controlled trials were included in the rapid review. On average, Orlistat results in obese people losing an additional 3–4% of their initial body weight over diet alone during a 2 year period. There was no strong evidence that this short-term weight loss would have a longer-term impact on morbidity and mortality. The cost utility of Orlistat treatment was estimated at around £46 000 per Quality Adjusted Life Year gained (extreme values sensitivity analysis £14 000 to £132 000). This rapid review raises some important questions about the potential value of Orlistat in the treatment of obesity. Further research is needed, not only to clarify the longer-term impact of Orlistat treatment, but also to uncover the longer-term impact on mortality and morbidity from short-term weight loss.