Cryptorchidism is a frequent abnormality which affects approximately 1% of children at age 1 year. Many nonscrotal testes are retractile and require no therapy. The pathogenesis remains controversial and involves possible mechanical, dysgenetic or hormonal factors. The latter are consistent with a partial defect in the hypothalamo-pituitary-gonadal axis, which may cause progressive histologic alterations in the testes after the first 6 months of life. Ultrasound is the simplest diagnostic technique (after clinical examination) to identify the testes in the inguinal region, while Magnetic Resonance Imaging can be performed to visualize abdominal testes. Therapy is still a matter of controversy. Hormonal treatments with HCG, LHRH or both should be used as first-intention treatment and their efficacy ranges from 0% to 60% in the various studies. LHRH nasal spray seems less effective if used alone. An early surgical treatment is recommended if the gonad is in the abdomen or close to the internal inguinal ring. The risk of cancer is increased in subjects with a history of cryptorchidism and even includes the contralateral descended testes. Early orchidopexy is not associated with a certain decrease of the risk. Cancer can be prevented by searching for in situ carcinoma with a biopsy performed after puberty. Fertility is impaired mainly in men with a history of bilateral cryptorchidism. There is weak evidence that early orchidopexy may improve fertility rates.