An experimental study was done in ten dogs and eight monkeys to evaluate the accuracy of dynamic and pharmacologic cavernosometry and cavernosography in the diagnosis of venogenic impotence. Our findings show that erection induced by saline perfusion comes about because the penile venous outflow capacity is exceeded. Thus, the cavernous occlusive mechanisms are not activated. Cavernosography in induced erection always demonstrated the entire cavernous venous system. However, cavernosometry after pharmacologic cavernous smooth muscle relaxation provides useful diagnostic information. Similarly, cavernosography after pharmacologic cavernous smooth muscle relaxation proved to be useful for the identification of abnormally draining veins.