Cryptorchidism is the most common male sexual disorder. In the case of an abdominal testis there is no objective criterion to choose between autotransplantation or orchiopexy after ligation of the spermatic vessels with. subsequent development of collateral blood supply, By combining near infrared spectroscopy (NIRS) with pulse oximetry the active testicular blood volume (ATBV) before and after occlusion of the spermatic vessels can be calculated in an animal model. NIRS is a noninvasive continuous optical technique that measures tissue oxygenation and hemodynamics. Ten boars with one nonpalpable testis each were selected. The spermatic vessels and vas deferens were separately prepared and atraumatic occluders were placed around the vessels. ATBV was measured before and after occlusion of the spermatic vessels. The calculated ATBV was 18.3 ± 2.3 ml/100 g of testicular tissue, not corrected by division by the path length factor, accounting for light scattering in the tissue. In 5 of 10 boars no significant ATBV was found after occlusion of the spermatic vessels, suggesting subsequent atrophy. NIRS combined with pulse oximetry provides us with reproducible quantification of ATBV. The method can be used to investigate the viability of a testis after (temporary) occlusion of the spermatic vessels.