: The value of adding testosterone to hormone therapy (HT) for the management of peri- and postmenopausal women is controversial and has not been systematically reviewed.: To determine the benefits and risks of testosterone therapy for peri- and postmenopausal women taking hormone therapy.: We searched the Cochrane Menstrual Disorders and Subfertility Group Trials Register (1st November 2003), The Cochrane Library (Issue 2, 2003), MEDLINE (1966 to 1st November 2003), EMBASE (1980 to 1st November 2003), Biological Abstracts (1969 to 2002), PsycINFO (1972 to 1st November 2003), CINAHL (1982 to 1st November 2003), and reference lists of articles. We also contacted pharmaceutical companies and researchers in the field.: Studies that were randomized comparisons of testosterone plus hormone therapy versus hormone therapy alone in peri- or postmenopausal women.: Two review authors assessed the quality of the trials and extracted data independently. Where it was necessary, the corresponding authors of eligible trials were contacted for additional information. For dichotomous outcomes Peto odds ratios and 95% confidence intervals were calculated. For continuous outcomes non-skewed data from valid scales were synthesized using a weighted mean difference or standardized mean difference. If statistical heterogeneity was found, a random-effects model was used and reasons for the heterogeneity were explored and discussed.: Twenty-three trials with 1957 participants were included in the review. The median study duration was 6 months (range 1.5 to 24 months). Most of the trials were of adequate quality with regard to randomization and concealment of allocation sequence. The major methodological limitations were attrition bias and lack of a washout period in the cross-over studies. The pooled estimate from the studies suggested that the addition of testosterone to HT regimens improved sexual function scores for postmenopausal women. A significant adverse effect was a decrease in high-density lipoprotein (HDL) cholesterol levels. The discontinuation rate was not significantly greater with testosterone therapy (Peto odds ratio 1.01, 95% confidence interval 0.76 to 1.33) than with HT alone. There was insufficient evidence of a treatment effect for perimenopausal women or for other outcomes.: Only a limited number of studies could be pooled in the meta-analyses. This limited the power of the meta-analysis to provide conclusions about efficacy and safety. However, there is evidence that adding testosterone to HT has a beneficial effect on sexual function in postmenopausal women. There was a reduction in HDL cholesterol associated with the addition of testosterone to the HT regimens. The meta-analysis combined studies using different testosterone regimens. It is, therefore, difficult to estimate the effect of testosterone on sexual function in association with any individual hormone treatment regimen.