Systematic reviews are increasingly used to combine the results of several studies in order to define the treatment effect with a high degree of precision. However, reviews of this nature may lead to spurious results and should not be accepted uncritically. This article, the second in a series on evidence-based psychopharmacology, is intended to illustrate the process of critical appraisal of a systematic review. In this example, a systematic review of studies comparing risperidone with conventional antipsychotics is appraised. Interpretation of the results of the systematic review may be hampered by the way in which studies were selected.