BACKGROUND: Heavy menstrual bleeding (HMB) is an important cause of ill health in premenopausal women. Although surgery is often used as a treatment, a range of medical therapies are also available. Nonsteroidal anti-inflammatory drugs reduce prostaglandin levels which are elevated in women with excessive menstrual bleeding and also may have a beneficial effect on dysmenorrhoea. OBJECTIVES: The primary objective of this review was to investigate the effectiveness of non-steroidal anti-inflammatory drugs (NSAIDs) in achieving a reduction in menstrual blood loss in women of reproductive years HMB. SEARCH STRATEGY: Electronic searches for relevant randomised controlled trials of the Cochrane Menstrual Disorders and Subfertility Group Specialised Register of controlled trials, MEDLINE, EMBASE, Current Contents, the Cochrane Library and CINAHL were performed. Attempts were also made to identify trials from citation lists of review articles and drug companies were approached for unpublished data. In most cases, the first author of each included trial was contacted for additional information. An updated search was performed in September and October 2001 but no new eligible trials were identified. SELECTION CRITERIA: The inclusion criteria were randomised comparisons of individual NSAIDs with either each other, placebo or other medical treatments in women with regular heavy periods measured either objectively or subjectively and with no pathological or iatrogenic (treatment induced) causes for their heavy menstrual blood loss. DATA COLLECTION AND ANALYSIS: Sixteen RCTs were identified that fulfilled the inclusion criteria for this review and data were extracted independently. Odds ratios for dichotomous outcomes and weighted mean differences for continuous outcomes were estimated from the data of nine trials. The results of the remaining seven crossover trials with data unsuitable for pooling were described in the Other Data section. MAIN RESULTS: As a group, NSAIDs were more effective than placebo at reducing heavy menstrual bleeding but less effective than either tranexamic acid or danazol. Treatment with danazol caused a shorter duration of menstruation and more adverse events than NSAIDs but this did not appear to affect the acceptability of treatment. There were no statistically significant differences between NSAIDs and the other treatments (oral luteal progestogen, ethamsylate, progesterone releasing intra-uterine system (IUS), oral contraceptive pill (OCC)) but most studies were underpowered. There was no evidence of a difference between the individual NSAIDs (naproxen and mefenamic acid) in reducing HMB. REVIEWER'S CONCLUSIONS: NSAIDs reduce HMB when compared with placebo but are less effective than either tranexamic acid or danazol. However, adverse events are more severe with danazol therapy. In the limited number of small studies suitable for evaluation, no significant difference in efficacy was demonstrated between NSAIDs and other medical treatments such as oral luteal progestogen, ethamsylate, OCC or IUS.