The length changes of the flaccid penis provoked by a maximum manual stretching of the glans have been measured in 905 men in order to study its biomechanical qualities. Our study shows that the flaccid penis is deformable, extensible and elastic in its longitudinal axis. The analysis of the variations of these biomechanical properties with aging shows a significant decrease. Thus, the biomechanical behavior of the flaccid penis during stretching is highly different in young men and old men. This distortion difference according to age proves the physiological importance of the penile distortion since impotence significantly increases with age. As the vascular mechanisms may be disregarded during flaccidity, these penile physical features of the flaccid penis are only due to tissue mechanisms. Consequently, any distortion loss would reflect a tissue impairment, very likely a progressive senile fibrosis of cavernous tissues.