Undescended testis is the most frequent disorder of male sexual differentiation affecting 0.8% of all boys by age 1 year. Anatomical and descriptive features of undescended testis lack standardization, and often do not reflect intraoperative findings. We review a large cohort of patients treated for undescended testis and analyze anatomical, morphological and volumetric findings at orchiopexy. Of 759 patients 1 month to 9 years old entered into the study between 1985 and 1990 at our hospital 55% underwent surgery between ages 8 months and 4 years, 15.5% had bilateral undescended testis and 27.6% had a nonpalpable gonad. Preoperative physical findings correlated poorly with intraoperative observation with respect to testicular position. An ectopic gonad was diagnosed in 15% of the patients, most of whom had a patent processus vaginalis. Gubernacular attachment was in the scrotum in only a third of all cases studied. Undescended testes were softer and smaller than the contralateral gonad in the majority of cases. To our knowledge ours is the first study to correlate preoperative and intraoperative findings in cases of undescended testis. New anatomical as well as morphological and volumetric data are provided.