OBJECTIVE:To assess the use of the International Index of Erectile Function (IIEF), routinely used in patients being treated for localized prostate cancer, including potency-preserving, nerve-sparing radical prostatectomy (RP), as many patients complain that the results of the IIEF over 4 weeks before RP are not representative. PATIENTS AND METHODS:The study included 123 consecutive patients (mean age 64.6 years, range 52-78) who had endoscopic-extraperitoneal RP and who completed the IIEF. The interval between the diagnosis of the disease and surgery was >4 weeks in all. The patients completed the same questionnaire referring to the last 4 weeks before their prostate biopsy, as a modified index of their sexual status (IIEFm and EFm). RESULTS:The clinical stage of disease was cT1c (34.9%), cT2a (49.5%), cT2b (5.7%) and cT2c (9.9%) before RP. The mean IIEF score was 42.8 and the mean EF domain score was 16.9; the mean IIEFm was 54.9 and the EFm domain score was 23.7. All the differences were statistically significant (P < 0.001). CONCLUSION:The IIEF questionnaire scores are influenced by many factors. Depression after a diagnosis of cancer, and the prostate biopsy-related symptoms, e.g. prostatitis, perineal pain and haemospermia, might compromise the patients' well-being and libido, and thus affect the IIEF scores before RP. We therefore suggest using the IIEFm and EFm scores before prostate biopsy to assess the patients' sexual status before any treatment for localized prostate cancer.