BACKGROUND: This study was performed to determine whether serial vertical sectioning of scalp biopsies increases the histological diagnostic yield in alopecias. MATERIALS AND METHODS: The study group included 100 consecutively referred patients with scalp alopecias. The formalin-fixed paraffin-embedded specimens of the scalp alopecias were completely serially sectioned in a vertical orientation and stained with haematoxylin and eosin. The histological diagnosis rendered in the initial slide harbouring three to six sections was compared with the diagnosis in the following vertical serial sections (30-116 serial sections per specimen, mean 53). RESULTS: A total of 55 scalp biopsies were classified histologically as non-cicatricial alopecia, 35 as cicatricial alopecia and 10 as 'others'. Diagnostic histological findings were present in the initial sections of 50 (50%) cases of alopecia, and only in the following serial sections in 48 (48%) cases. Two cases (2%) lacked differentiating diagnostic histological features in all of the vertical sections. The diagnostic yield of the serial vertical sections compared with the initial sections was higher in the non-cicatricial alopecias (52.7%) than in the cicatricial alopecias (48.5%) and the 'others' category (10%). CONCLUSIONS: Serial vertical sectioning of scalp alopecias increases the histological diagnostic yield, substantially.