In order to evaluate the impact of minor surgery on platelet aggregability and the effect of anaesthesia on this parameter, we allocated 14 otherwise healthy men for inguinal herniotomy to either general anaesthesia (n = 7) or lumbar epidural anaesthesia (n = 7). Platelet aggregation threshold to adenosine diphosphate (ADP-threshold) was measured before and after anaesthesia, prior to surgery, at the end of surgery and during the following hours as well as on the first post-operative morning. General anaesthesia did not affect ADP-threshold while epidural analgesia itself induced a significant increase. During and soon after surgery the ADP-threshold increased in those receiving general anaesthesia while in those receiving epidural analgesia the ADP-threshold returned to pre-operative levels. On the first post-operative morning both groups showed a significantly lower ADP-threshold as compared to the pre-operative level. Surgery induced an increase in 3'5' cyclic-adenosine monophosphate (cAMP). This adrenergic response was attenuated by epidural analgesia.