There is currently controversy on whether the insufficient response to penile venous surgery done in an attempt to restore erectile function is due to recurrent or residual veins. In order to elucidate this issue, we report a study on those patients who failed to respond to the first venous surgery and subsequently underwent or declined a second operation. From July 1996 to July 2003, a total of 83 patients, aged 25 to 83, who were dissatisfied with their first venous surgery and were later diagnosed with a persistent veno-occlusive dysfunction via our dual cavernosography, were recruited into our study. Subsequently, 45 men underwent penile venous stripping surgery for a second time and were assigned to the surgery group, whereas the remaining 38 men were subject to follow-up and routine management and were assigned to the control group. All were evaluated with the abridged 5-item version of the international index of erectile function (IIEF-5) every 6 months for 1 to 5 years and cavernosogram, if necessary. In the surgery group their preoperative IIEF-5 score was 10.1 +/- 3.7, which increased to 17.1 +/- 3.2 (P < .001) after the first surgery and further increased to 20.7 +/- 3.1 (P < .001) after a second venous stripping of the cavernosal vein that was consistently demonstrated on the cavernosogram. Overall, 41 men (91.1%) reported a positive response to further venous surgery, with more satisfactory coitus, after the residual veins were stripped thoroughly, although eventually 4, 3, and 3 men required additional oral sildenafil, penile implant, and intracavernosal injection, respectively. The follow-up period ranged from 12 months to 72 months, with an average of 37.0 +/- 11.5 months. In the control group, however, their corresponding IIEF-5 score changed from 17.4 +/- 2.9 to 16.9 +/- 3.2 (P > .05). Finally, 11, 7, and 8 men required additional oral sildenafil, penile implant, and intracavernosal injection, respectively. Although there was no statistical significance between the 2 groups in the first postoperative IIEF-5 scores, there was a significant difference in their IIEF-5 after further venous surgery. In this study, we propose that the clinical relapse of erectile dysfunction is a result of "residual" veins rather than "recurrent" ones.