In children with nonpalpable undescended testes, preoperative localization is very helpful prior to surgical investigation both to reduce the time required for complete exploration and to plan the correct surgical procedure. Magnetic resonance imaging (MRI) was accomplished in 23 patients with a clinical diagnosis of cryptorchidism after ultrasonographic studies were inconclusive in identifying the undescended testis. An abdominal testis was correctly located in 16 cases. No structures resembling testicular parenchyma were detected in 4 instances. The surgical findings confirmed the absence of testes in 2 patients but showed 2 abdominal testes not seen by MRI. The movements of 5 patients caused inadequate MRI examinations, so these patients were not considered in the results. In our experience MRI proved to be effective in locating undescended abdominal testes with a diagnostic accuracy of 90%. Therefore MRI should be performed before any invasive diagnostic procedure. Lack of cooperation in young patients could reduce the accuracy of the procedure, so we think that sedation should be performed in children under 6 years of age.