['We studied the ability of testis biopsy to predict eventual fertility potential.', 'A total of 25 patients with unilateral undescended testis and 11 with bilateral undescended testes who previously underwent orchiopexy at a median age of 9 years were followed until after age 18 years. Semen analysis, testicular volume, follicle-stimulating hormone, luteinizing hormone, testosterone and inhibin B were compared to previously obtained biopsies of each testis. Biopsies were graded as mild, moderate or severe histology based on published data for normal and undescended testis histology.', 'Patients with unilateral undescended testis and moderate histology were more likely to have a sperm density of greater than 20 million per cc than those with severe histology (p = 0.006), although no difference in hormonal parameters was noted. Patients with bilateral undescended testes and moderate histology were more likely to have normal follicle-stimulating hormone and inhibin B than those with severe histology (p = 0.05 and 0.002, respectively), although no difference in semen analysis was observed. Overall 7 of the 9 patients with bilateral undescended testes had less than 20 million sperm per cc.'] Does testis histopathology in boys with cryptorchidism correlate with future fertility potential?