Seborrheic keratoses and acrochordons may change in biologic behavior with pregnancy or during treatment with sex steroids. Because epidermal growth factor receptor localization may change in hyperproliferative skin diseases, we compared epidermal growth factor receptor immunolocalization in seborrheic keratoses and acrochordons from women who were or were not pregnant or taking oral sex steroid hormones. Epidermal growth factor receptor was further investigated in growing and quiescent seborrheic keratoses and acrochordons from women with and without the dysplastic nevus syndrome. The epidermal growth factor receptor concentration was strikingly elevated in suprabasilar keratinocytes of growing seborrheic keratoses and acrochordons from patients with the dysplastic nevus syndrome who were pregnant or taking sex steroid hormones and less elevated in growing seborrheic keratoses from other patients. In contrast, the epidermal growth factor receptor distribution pattern in acrochordons did not correlate as well with the history of growth of these lesions in normal patients. These data suggest sex steroids may affect epidermal growth factor receptor metabolism in benign epidermal hyperproliferative lesions, particularly in patients with the dysplastic nevus syndrome.