Ropivacaine is a new aminoamide local anaesthetic agent. Unlike other agents in its class, such as bupivacaine, it has been found to be vasoconstrictive. We have sought to investigate if this property is clinically useful and may reduce surgical blood loss. Reduction mammoplasty is a procedure in which considerable blood loss may occur. We have compared pre-incision infiltration of ropivacaine 75 mg in 0.9% saline 60 ml with the current practice of infiltration with bupivacaine 75 mg in 0.9% saline 60 ml and epinephrine (adrenaline) 5 micrograms ml-1. We studied five subjects; each received both solutions by infiltration, one to each breast, in random order and both the operating surgeon and anaesthetist were blind to the solution given. For data analysis, blood loss was expressed in ml/kg of tissue excised. There was no significant difference between the two regimens for duration of surgery or amount of tissue excised; however, ropivacaine was associated with markedly greater intraoperative blood loss than bupivacaine (median 696 (range 305-1366) ml kg-1 vs 300 (169-608) ml kg-1; P = 0.04, Wilcoxon rank sum test). Postoperative blood loss was not significantly different between groups (116 (14-173) ml kg-1 vs 98 (13-332) ml kg-1; P = 0.69, Wilcoxon rank sum test). We conclude that the vasoconstrictive properties of ropivacaine were not sufficiently great to merit its use as a sole agent for infiltration before reduction mammoplasty.