ColorDoppler Ultrasound (CDU) is one of the principle methods in the post-operative diagnosis of recurring varicoceles. Aim of this study was valuate modifications of seminal parameters related to scrotal CDU results. In order to clarify varicoceles effect on fertility, these parameters have been related to pregnancy rate. We have studied 93 patients with varicoceles, undergone to venous "en bloch" legature from november 1994 to december 2000. Recurrence rate was 3.1% at post-operative scrotal CDU after 3 months. In patient with negative CDU, seminal quality improved (statistically significant results) and pregnancy rate was 41.4%. CDU has an important role in varicoceles, both at diagnosis and in post-operative follow-up. It is a quick and simple test, non-invasive and well-tolerated by patients. If associated with spermiogram, it is useful in order to show post-operative recurrences and surgical complications in patients treated with varicocelectomy.