Varicocele, whose association with male infertility has been clearly documented in the literature, is a common finding in adolescents and adult men, being diagnosed in 20-40% of infertile patients. A correct and early diagnosis of this affliction is of great importance because, in most cases, a timely correction, usually performed using percutaneous sclerotherapy, leads to an improvement in semen quality. Currently, physical examination in a warm room is the mainstay of diagnosis, but this is affected by a low sensibility and specificity, especially in cases of low grade varicocele. Colour Doppler ultrasound (CDU) is a new, reliable and non-invasive diagnostic method for the evaluation of varicocele testes which allows the detection of even subclinical varicocele thanks to its capacity for measuring the size of the pampiniformis plexus and blood flow parameters of the spermatic veins. At present, there is a lack of completely standardised diagnostic criteria, but when this problem is solved, clinical examination and CDU will certainly become the "gold standard" in the investigation of varicocele.