Cryptorchidism affects approximately 1 in 150 boys. Non-palpable testes represent nearly 20% of all cases. If present, they are situated between the inferior renal pole and the external inguinal ring. Often at surgical exploration, however, a "nubbin" of testicular tissue is found at the end of blind ending spermatic vessels without demonstration of a recognizable testis; this finding is referred to as an absent testis. In other patients, no vascular or ductular (epididymis-vas deferens) or even testicular structure can be observed. This situation defines true testicular agenesis. Non-palpable testes have an increased risk of malignant transformation, infertility, associated inguinal hernia and congenital ductular abnormalities. Surgical treatment is often more complex and unsuccessful. Many imaging diagnostic methods to investigate patients with non-palpable testes (pneumoperitoneography, angiography, ultrasonography, CT scan and RMN) have been used so far but none of these has been uniformly accepted as the ideal investigative technique because they are unreliable and/or they involve a fair risk. Since Cortesi and associates first described in 1976 a case of abdominal testes identified by laparoscopy, this technique has gained increased acceptance by pediatric urologists and surgeons. Today, celioscopy plays a central role in the exploration of non-palpable cryptorchid testes. The authors try to establish an algorithm methodology for investigating non-palpable testes under the light of recently reported anatomical, pathological and surgical data.