The influence of prazosin on experimental vein graft intimal thickening was studied in a rat model. The iliolumbar vein was grafted into the common iliac artery in a prazosin-treated group (n = 17) and a control group (n = 23). Three weeks after grafting the animals were killed and the grafts harvested. Longitudinal sections were prepared and the intimal thickness measured in the proximal, mid and distal graft. Intimal thickness varied considerably in both groups. Median (range) intimal thicknesses for the control group were: proximal 50 (10-120)-mu-m; mid 30 (10-70)-mu-m; and distal graft 30 (10-100)-mu-m. Results for the prazosin-treated group were: proximal 70 (10-160)-mu-m; mid 25 (5-60)-mu-m; and distal graft 25 (5-135)-mu-m. There was no statistically significant difference in median intimal thicknesses between the control and treated groups.