Secondary cryptorchidism was investigated after hernia repair in 15 patients 1 month to 7 years old. Testicular biopsy was obtained during orchiopexy. The number of spermatogonia per tubular cross section was higher in these patients than in boys with primary cryptorchidism, and the differences were significantly greater when the period of cryptorchidism was longer than 5 years. Loss of germ cells in secondary cryptorchidism was lower than in primary cryptorchidism. The spermatogonia per tubular cross section ratios were at the same low level in both groups in adolescence. These differences between primary and secondary cryptorchidism can be due to a lack of testicular exocrine function after a normal priming effect when the testes are in descended position. Collagenization of the peri-tubular connective tissue and the lack of germ cells are the only histological changes that occur in secondary cryptorchid testes when they have remained in cryptorchid position for 2 years, which is in marked contrast to primary cryptorchid testes that did not receive the priming effect in the first months of life. However, fertility is influenced minimally due to the presumably normal functioning of the contralateral testicle. Secondary cryptorchid testes demonstrate significant dysfunction after 5 years in that position. Germ cell loss occurs more slowly in secondary than in primary cryptorchidism. Despite the optimistic prognosis for fertility, we recommend early orchiopexy for secondary cryptorchidism to prevent exocrine insufficiency of the affected testicle.