PURPOSE Androgen stimulation before hypospadias surgery has resulted in increased penile size, fewer complications and improved cosmesis, and suggests increased neovascularization. To our knowledge the real effect on neovascularization remains to be proved. We studied the histological effects of testosterone on neovascularization. MATERIALS AND METHODS A total of 26 boys with hypospadias were randomly allocated to 2 groups before surgical correction. Group 1 did not receive any treatment and group 2 received 1% testosterone propionate ointment twice daily for 30 days before surgery. During the surgical procedure a fragment of prepuce was excised and prepared for histological evaluation. The number and volume density of blood vessels were determined by labeling for von Willebrand's factor. Blood vessel quantification as volume density was done using a video microscopy system with a superimposed cycloid arch test system. RESULTS The groups were similar in age and hypospadias classification. Testosterone treated prepuces (group 2) had an increased absolute number of blood vessels (mean ± SD 8.5 ± 1.3 vs 4.8 ± 1.8 vessels per field) and increased blood vessel volume density (mean 50.5% ± 7.8% vs 24.8% ± 8.6% vessels per point) (each p <0.001) compared to those in untreated patients (group 1). CONCLUSIONS The use of 1% testosterone propionate ointment before hypospadias surgery produces neovascularization in absolute numbers and in volume density.