Ultrasound (US) has become crucial in the assessment of infertility of couples, in 50% of whom the male partner is responsible. Male infertility is caused by many diverse conditions, from reparable obstructive disorders to noncorrectable intrinsic testicular failure. During the past 4 years, a select group of 70 young infertile men with azoospermia or oligospermia and low ejaculate volume were examined with transrectal US. Twenty-six patients had congenital bilateral absence of the vas deferens, 11 had congenital unilateral absence of the vas deferens and contralateral obstructive pathology, 15 had additional abnormalities thought to be directly related to semen deficiencies, and 18 patients with other causes for semen deficiency and infertility had findings that were either normal or showed minor abnormalities. The delineation of congenital and obstructive abnormalities of the distal urogenital tract with transrectal US enables an accurate diagnosis of certain cases of male infertility and helps guide appropriate clinical and surgical management.