To test the neourethra objectively in cases judged to be clinical successes after transverse island flap hypospadias repair, we analyzed uroflowmetry data (peak flow, voided volume and ultrasonically determined post-void residuals) after repair. Patients were included if they were old enough to void volitionally and flow data were available after fistula or stricture repair. Flow data were then plotted on previously published age-dependent nomograms from normal controls. Of 80 boys available for study 51 required no secondary procedures, 16 subsequently underwent fistula repair and 13 had strictures opened. After all primary and secondary procedures 55 patients (69%) had peak flows within the normal range and 25 (31%) had peak flows below the normal range. Of the 51 boys who never had fistulas and/or strictures 37 (73%) had normal flows while 18 of 29 (62%) who underwent fistula and/or stricture repairs had normal flows (p < 0.05). Residual volume was less than 10% of voided volume in 44 of the 51 boys who clinically had no problems postoperatively, in 8 of the 13 who had strictures opened and in 15 of the 16 who underwent fistula repairs. We conclude that the neourethra is functionally equivalent to a normal urethra in most boys after transverse flap urethroplasty. A majority of boys will have normal flow even after stricture or fistula repair.