Cryptorchidism or undescended testis is considered to be the most common endocrinological disease in male newborns. During fetal life, the testes have to migrate from the abdomen through the inguinal canal down to the scrotum. This testicular descent usually finishes around the 35th week of gestation. Therefore, according to gestational age incidence is variable and affects 1.0–4.6% of full-term and up to 45% of preterm neonates. In addition, this congenital malformation may affect both sides in up to 30% of individuals. The conditions related to undescended testes have been studied quite extensively from the clinical as well as experimental point of view. Still, the underlying causes are poorly understood since cryptorchidism obviously represents a multifactorial disorder. Although advances in the medical and surgical treatment of undescended testes are quite substantial, areas of clinical controversies are still present. The possible consequences of failure or delay of treatment can be substantial. Impaired fertility and/or increased testicular cancer risk in adulthood represent the two most important sequelae. These risks can be minimalized when proper diagnosis and successful treatment are carried out early enough and finished before 12 months of age, with 18 months at the latest.