Objectives : To determine the penile size in adult Egyptians and toclarify the relationship between fully stretched penile measurements innormal subjects and erectile dysfunction patients.Methods : This study included 1027 adult Egyptians presenting toKasr El-Aini outpatient clinic. Two groups of patients were included in thisresearch work. Group one, normal adults (949) and Group two, erectiledysfunction patients (78). There were no differentiation of race, age, heightand weight. Penile length and girth were measured using a ruler and a tapemeasurerespectively, in the fully stretched states in both groups. All penilemeasurements were performed by the same physician.Results : In group one : The mean of fully stretched length was 12.9 ±1.9 cm and the mean of fully stretched girth was 8.9 ± 0.9 cm.In group two : The mean of fully stretched length was 11.2 ± 1.5 cmand the mean of fully stretched girth was 8.8 ± 0.8 cm. Comparing themean of fully stretched penile lengths in both groups revealed statisticallysignificant difference (P<0.001) between them, while comparing the meanof fully stretched penile girths in both groups revealed statistically nonsignificantdifference (P=0.474) between them. There was significantpositive correlations between fully stretched penile lengths and fullystretched penile girths in both groups.Conclusion : The average of fully stretched penile length in normalpotent Egyptians is 12.9 cm, while the patients with erectile dysfunctiontend to have significantly shorter penises (11.2 1.5 cm).