The role of endothelin-1, a potent vasoconstrictor released by vascular endothelium, in the vasoconstriction that develops after prolonged operations is not clear. This study was performed in order to determine if there was any relationship between endothelin-1 and the degree of vasoconstriction during prolonged plastic surgery. Plasma concentrations of endothelin-1, skin-forearm temperature gradient (Tgrad), rectal temperature, mean arterial pressure (MAP) and heart rate (HR) were measured at nine predetermined times before, during and after operation in nine women undergoing breast reconstruction with a pedicled transverse rectus abdominis musculocutaneous flap. Development of cutaneous or fat necrosis of the flap was assessed clinically and with ultrasound. Concentrations of endothelin-1 before induction were increased (median 8.9 (25-75% quartiles 5.5-12.5) pg ml-1). During operation they were approximately 3 pg ml-1 and after operation approximately 5 pg ml-1. Tgrad was approximately 4 degrees C before induction and after operation, indicating marked vasoconstriction; during operation it was about zero, indicating vasodilatation. There was a statistically significant correlation between endothelin-1 concentrations and Tgrad (Spearman non-linear correlation) (r = 0.32, P = 0.004) and between endothelin-1 and MAP (r = 0.25, P = 0.02), but not between endothelin-1 and HR or development of minor cutaneous or fat necrosis of the flap (five patients). We conclude that increased plasma concentration of endothelin-1 is associated with the extent of peripheral vasoconstriction.