Laryngeal squamous cell carcinomas from 15 consecutive preoperatively irradiated patients were investigated for the expression of epidermal growth factor receptor (EGF receptor). The study was performed on frozen sections by means of the 5-layer APAAP technique employing an antibody recognizing the extracellular part of the EGF receptor. In sections from 9 of the patients with laryngeal squamous cell carcinoma, normal differentiated epithelia were included. Sections from 6 of these patients, in addition, contained dysplastic epithelia. Expression of EGF receptor-like material was demonstrated in the basal cell layer of normally differentiated laryngeal epithelial and in dysplastic epithelia. Fourteen of the squamous cell carcinomas proved EGF receptor positive. Nearly all cells in the poorly differentiated carcinomas showed positive staining with the antibodies. In moderately to well differentiated carcinomas a reduction in the extent of staining was seen in certain areas. Especially for the epithelial pearls, the staining reaction was localized to the undifferentiated cells in the periphery. This finding corresponds to the staining pattern observed in the basal cell layers of normal epithelial. The present investigation confirms the expression of EGF receptor-like material in normal laryngeal epithelial, dysplastic epithelial and squamous cell carcinoma. The staining pattern was similar to that observed in oral squamous cell carcinomas, predominantly varying inversely with cellular differentiation.