Abdominal CT examinations of 40 patients with non-seminomatous testicular tumors were reviewed with previous knowledge of the side of the testicular primary. Metastatic nodes, between 1.5 cm and 2.0 cm in diameter were overlooked more frequently in patients with right than in those with left testicular primaries, because mildly enlarged aorto-caval or para-caval nodes (which are the most frequent site of metastasis from a right testicular lesion) were more difficult to detect than enlarged left para-aortic lymph nodes. Efforts to delineate the aorto-caval region on CT examinations of patients with right-sided lesions must be increased in order to reduce a surprisingly high false negative rate.