Spontaneous descent of testes after birth can occur in up to 70% of cases, yet the factors contributing to it are still controversial. This study aims to evaluate factors contributing to spontaneous descent of palpable undescended testes. Eighty-four newborns with 126 palpable undescended testes (42 unilateral and 42 bilateral) were followed up for a period of one year to study the occurrence and time of testicular descent and its relation to gestational age, birth weight, uni- or bilaterality and levels of FSH, LH and testosterone. A total of 58 testes (46%) descended between 3 and 6 months. Spontaneous descent occurred in 10 premature patients (14 testes 63%) compared to 44 testes of full-term patients (43%). Descent occurred in 14 unilateral undescended testes (33%) compared to 44 (52%) in bilateral cases. In patients with spontaneous testicular descent there was postnatal peak of LH and testosterone at 2 to 3 months of age which returned to basal level at 6 months of age. In patients with permanent undescended testes the peak of LH and testosterone was very low and almost absent in some of them; no significant difference was found between the mean values of FSH in both groups. No spontaneous testicular descent occurred after the 4th month in the full-term group, whereas in the pre-term group spontaneous descent occurred up to 6 months of age. This study concluded that spontaneous descent of palpable undescended testes is closely related to the presence of LH and testosterone surge. Therapy of undescended testes should start at 4 months of age in a full-term baby and at 6 months of age in a pre-term baby.