A varicocele consists of a group of dilated veins in the spermatic cord and pampiniform plexus, almost exclusively on the left side. Varicoceles occur more commonly in infertile men than in the rest of the population. On ultrasound (US), varicoceles appear as tubular, serpiginous structures larger than 2–3 mm in diameter along the course of the spermatic cord or in the peritesticular region, typically above and posterior to the testis. Color Doppler US is helpful in confirming the presence of a varicocele and detecting a subclinical varicocele. Varicocele may extend into the testicle resulting in intratesticular varicocele, which can be depicted by color Doppler US. Internal spermatic venography seems to be the most sensitive test to detect reflux. The major venographic finding of varicocele is free retrograde flow of contrast material into the dilated pampiniform plexus. Treatment is indicated if varicoceles are large and symptomatic and in subfertile men with clinical or subclinical varicoceles who have been infertile for at least 2 years and who have oligoasthenospermia without an apparent cause of infertility. Treatment of varicocele is either by surgical ligation or by transcatheter occlusion of the internal spermatic vein.