Thromboxane A2 is a potent vasoconstrictor and a stimulus of platelet aggregation, which may contribute to hypercoagulability. The prostacyclin, prostaglandin I2, has exactly the opposite effect. Measurement of the major urinary metabolites, 11-dehydro-thromboxane B2 and 2,3-dinor-6-keto-prostaglandin F1 alpha (prostaglandin F1 alpha) by radioimmunoassay can accurately reflect in vivo the biosynthesis of thromboxane A2 and prostaglandin I2, respectively. Group 1 consisted of 60 patients less than 50 years old. The mean urinary 11-dehydro-thromboxane B2 level of 3 patients with arteriogenic impotence was significantly greater than that of the 57 control volunteers: 2.66 +/- 0.65 versus 1.74 +/- 0.56 (plus or minus standard deviation) ng./mg. creatinine (p = 0.008). The prostaglandin F1 alpha levels for the patients and controls were 32.74 +/- 8.45 and 37.58 +/- 16.55 ng./mg. creatinine, respectively, which was not significantly different (p greater than 0.05). Group 2 consisted of 96 patients 50 years old or older. The 11-dehydro-thromboxane B2 concentration in the urine was 1.83 +/- 0.58, 2.54 +/- 1.12 and 1.91 +/- 0.73 ng./mg. creatinine in the 47 normal control volunteers, 20 patients with arteriogenic impotence and 29 with arteriogenic impotence plus intracavernous injection of 20 micrograms prostaglandin E1, respectively. The arteriogenic impotence group showed the significantly highest level among the 3 groups (p = 0.0025). Also, the urinary prostaglandin F1 alpha levels in these patients were 45.71 +/- 36.3, 57.71 +/- 35.53 and 59.30 +/- 45.08 ng./mg. creatinine, respectively, which was not significantly different (p greater than 0.05). For the 13 patients with arteriogenic impotence (group 3) we compared the urinary 11-dehydro-thromboxane B2 and prostaglandin F1 alpha levels before and after intracavernous injection of prostaglandin E1 by using a paired t test. The results showed that the change in 11-dehydro-thromboxane B2 levels was 2.78 +/- 1.09 versus 1.99 +/- 0.75 ng./mg. creatinine, which was significantly different (p = 0.005), whereas that for prostaglandin F1 alpha was 62.30 +/- 40.41 versus 58.86 +/- 44.26 ng./mg. creatinine, with no significant difference (p greater than 0.05). Our findings suggest that urinary 11-dehydro-thromboxane B2 may have an important role in the diagnosis and treatment of arteriogenic impotence.