Introduction/Aims: We have studied the natural history of Peyronie's disease with particular reference to erect (functional) penile length. To our knowledge this has so far not been documented.Methods: 21 men with stable Peyronie's deformity were followed up for 6 months when no active treatment was being offered. By inducing an artificial erection objective assessments of penile length and deformity were made on day 1 and at six months.Results: Measurable shortening in straight penile length was noticed in 6/21 (28.5%) of men (Mean: 0.92 cm), lengthening in 8/21 (38.09%) of men (Mean: 0.81 cm), while no change was noticed in the remaining 7 (33.3%).Angulation increased (worsened) in 5 (23.8%), decreased (improved) in 11 (52.38%) and showed no change in 5 (23.8%). There was no association between change in angle of deformity and change in penile length.Conclusions: In Peyronie's disease, a progressive reduction in penile length is noticed in up to a third of patients with stable disease and this is not necessarily associated with deteriorating angle of deformity.