An abridged five-item version of the 15-item International Index of Erectile Function (IIEF) was developed (IIEF-5) to diagnose the presence and severity of erectile dysfunction (ED). The five items selected were based on ability to identify the presence or absence of ED and on adherence to the National Institute of Health's definition of ED. These items focused on erectile function and intercourse satisfaction. For 1152 men (1036 with ED, 116 controls) analyzed, a receiver operating characteristic curve indicated that the IIEF-5 is an excellent diagnostic test. Based on equal misclassification rates of ED and no ED, a cutoff score of 21 (range of scores, 5-25) discriminated best (sensitivity=0.98, specificity=0. 88). ED was classified into five severity levels, ranging from none (22-25) through severe (5-7). Substantial agreement existed between the predicted and 'true' ED classes (weighted kappa=0.82). These data suggest that the IIEF-5 possesses favorable properties for detecting the presence and severity of ED.