Colour Doppler ultrasonography was used to assess 39 patients with Peyronie's disease with a suspected organic cause for their impotence. In 20 patients who complained of a uniform loss of erection, the impotence was likely to be functional in origin (90%) or occasionally venogenic (10%), the penile arterial blood flow being normal. However, patients who complained of distal flaccidity were likely to have an organic cause for their impotence (68%). This was due to proximal arterial disease (10%), plaque involvement of the distal vessels (37%), veno-occlusive dysfunction (5%) or to the soft glans syndrome (16%).