Objective: The diameters of the veins in the pampiniform plexus have been used to diagnose subclinical varicocele. But there are many cutoff points and some controversies about the diagnosis. These cause difficulty in the evaluation of the results of epidemiological and clinical studies. Our aim is to establish the reliability of vein diameters in the pampiniform plexus in the diagnosis of subclinical varicocele. Methods: Physical examination, scrotal gray scale ultrasonography (SU) and color Doppler ultrasonography (CDU) were performed to assess varicocele in 100 infertile patients without clinical varicocele (group I), 100 infertile patients with clinical left varicocele (group II), and 50 fertile men without clinical varicocele (group III) as a control group. The diameter of the veins in the pampiniform plexus was measured with SU. According to various cutoff points of venous diameter and CDU criteria, the diagnosis of varicocele was made. The highest mean venous diameters were calculated with and without varicocele in men whose diagnoses had been made with CDU. The results were correlated with each other and the control group. Results: According to venous diameter cutoff points, the varicocele ratio did not correlate with the CDU results (p < 0.05) except for the left side of patients with clinical left-sided varicocele. The highest mean diameters of the veins in group III (control group) did not show a significant difference to the other groups (p > 0.05) except for the left side of group II patients. We did not find an exact relation between the highest venous diameter in the men who have and those who do not have subclinical varicocele with CDU. The highest mean diameter was 2.17 +/- 0.34 (SD) mm for men who have subclinical varicocele and 2.00 +/- 0.31 mm for men who do not have subdinical varicocele by CDU (p < 0.05). Conclusion: Our results indicate that venous diameters should not be used as diagnostic criteria for subdinical varicocele. Only the evaluation of venous diameter in varicocele should be used to document and quantify pathology, but it should not be used to establish the diagnosis. Copyright (C) 2003 S. Karger AG, Basel.