Background: Fibrin sealants have become popular in improving perioperative haemostasis and reducing the need for allogeneic red cell transfusion. Methods: A systematic review of randomized controlled trials was conducted to examine the efficacy of fibrin sealants in reducing perioperative blood loss and allogeneic red blood cell transfusion. Studies were identified by computer searches of Medline, Embase, Current Contents, the Cochrane Library, manufacturer websites (to January 2001), and bibliographic searches of published articles. Trials were eligible for inclusion if they involved adult elective surgery and reported quantitative data on blood loss, the proportion of patients exposed to allogeneic red cell transfusion and/or the volume of blood transfused. Results: Twelve trials met the criteria for inclusion. Fibrin sealants reduced the rate of allogeneic blood transfusion (relative risk 0.40 (95 per cent confidence interval (c.i.) 0.26 to 0.61); five trials with 275 subjects) and reduced blood loss (weighted mean difference - 151.68 (95 per cent c.i. - 251.91 to - 51.46) ml; seven trials with 391 subjects). Generally, the trials were small and of poor methodological quality. Conclusion: Overall the results suggest that fibrin sealants are efficacious. Owing to lack of blinding, transfusion practices may have been influenced by knowledge of the patient's treatment status. This raises concern about blood transfusion practice as a response variable. Large methodologically rigorous trials of fibrin sealants with clinical outcomes are needed.