Recently it has been reported that there is a strict correlation between erectile dysfunction (ED) and cardiovascular diseases, but the importance of such relationship still needs to be addressed. Ultrasonographic peak systolic velocity (PSV), is considered a reliable parameter for the diagnosis of arteriogenic ED. However, the cut-off value of PSV<30 cm/s has sufficient sensitivity only in the diagnosis of advanced arteriogenic ED and it is not representative of peripheral vascular alterations. In the present study, we set up an age-adjustment of PSV - calculated with the formula PSV <6.73+age x 0.7 - that permits a more accurate diagnosis of vascular aetiology in ED patients and may predict the presence of carotid wall alterations. We studied 179 consecutive subjects (mean age 52 years, range 23-79 years), with a history of ED of at least 6 months, by means of penile colour doppler ultrasonography (P-CDU) and common carotid arteries colour doppler ultrasonography (CCA-CDU) between June 2003 and September 2004. Statistical analysis was carried out with the statistical software R. PSV and CCAD values showed a statistically significant negative correlation. Age adjustment further improved this relationship permitting to identify an age-dependent PSV cut-off given by the formula PSV <6.73+age x 0.7. The age-adjusted PSV cut-off allows an accurate interpretation of vascular aetiology in ED patients and predicts the presence of carotid wall alterations, from the intima-media pathologic thickness to the plaque formation, with high values of both sensitivity and specificity.