The purpose of this work was to determine penile size in adult normal (group one, 271) and impotent (group two, 109) Jordanian patients. Heights of the patients, the flaccid and fully stretched penile lengths were measured in centimeters in both groups. Midshaft circumference in the flaccid state was recorded in group one. Penile length in the fully erect penis was measured in group two. In group one mean midshaft circumference was 8.98+/-1.4, mean flaccid length was mean 9.3+/-1.9, and mean stretched length was 13.5+/-2.3. In group two, mean flaccid length was 7.7+/-1.3, and mean stretched length was 11.6+/-1.4. The mean of fully erect penile length after trimex injection was 11.8+/-1.5. In group 1 there was no correlation between height and flaccid length or stretched length, but there was a significant correlation between height and midpoint circumference, flaccid and stretched lengths, and between stretched lengths and midpoint circumference. In group 2 there was no correlation between height and flaccid, stretched, or fully erect lengths. On the other hand, there was a significant correlation between the flaccid, stretched and fully erect lengths. Comparing group 1 and group 2, the patients in group 1 were slightly older than in group 2 (P=0.035), but there was no significant difference in their height. However, there was a significant difference regarding the mean flaccid length 9.3 vs 7.7 (P=0.001), and the mean stretched length 13.5 vs 11.6 (P=0.000). We divided both groups into those who are less than 40 y of age, and over 40 y old. There was no statistical difference in the stretched and flaccid lengths between the younger and older individuals in each group. However, when we compared the stretched and flaccid lengths in those of less than 40 y old in group 1 and 2, a significant difference was noticed. Similarly, a significant difference in the stretched and flaccid lengths in those patients over 40 y of age was also present.