In a 5-years' study, we investigated the correlation between clinical and histological diagnoses of blue nevi. In 24.7% of the cases, the clinical diagnosis turned out to be false; blue nevus was mostly confused with nevomelanocytic nevus (11.2%). Malignant melanoma was the primary differential diagnosis in 13 out of 89 cases. Differentiation of the histological subtypes identified 76.4% of the tumors as common blue nevi and 15.7% as cellular blue nevi. The remaining 7.9% were combined nevi. The average age of the patients with blue nevi at the time of excision was lower than that of the patients suffering from malignant melanoma during the same observation period. Comparison of the distribution of 89 blue nevi with 196 malignant melanomas revealed the different preferred areas of these tumors. We briefly refer to related dermal melanocytoses, such as Mongolian spot and Ota's nevus.