The goal of our study was to determine the frequency of endocrine abnormalities in sexually mature men with mild hypospadias. For this purpose we evaluated 16 men 22 to 52 years old with mild hypospadias. All patients had a urethral meatus distal to the penoscrotal junction. Serum concentrations of luteinizing hormone, follicle-stimulating hormone and testosterone were measured in all subjects. Dihydrotestosterone and testosterone precursors also were determined in men who had abnormally elevated levels of luteinizing hormone. The level of serum luteinizing hormone in patients was significantly higher than that of normal men, whereas the levels of serum follicle-stimulating hormone and testosterone were similar to those of normal subjects. Of the 16 men with mild hypospadias 3 had abnormally elevated levels of gonadotropins: 2 had primary gonadal dysfunction (elevated luteinizing hormone and follicle-stimulating hormone with low or normal testosterone) and 1 had hormonal evidence of partial androgen insensitivity (elevated luteinizing hormone, normal follicle-stimulating hormone with high normal testosterone and dihydrotestosterone). These patients are rather unique, since they did not have other compromising factors to account for the gonadal failure. In summary, our data demonstrated the presence of endocrine dysfunction in men with mild hypospadias.