Ten cases each of lupus erythematosus (discoid or systemic, LE), pemphigus foliaceus (PF) and erythema multiforme (EM), seven cases of toxic epidermal necrolysis (TEN) and two specimens of normal canine skin have been evaluated for the presence of apoptotic cells by immunohistochemistry using a commercially available in situ apoptosis detection kit (ApopTag, Oncor). In normal skin sections cells located in the centre of sebaceous glands and in catagen hair follicles were stained. In TEN no epidermal cell was positive, whereas in LE scattered basal and low suprabasal cells stained, and in EM single suprabasal epidermal cells stained. In PF acantholytic cells were predominantly negative, but there were single positive suprabasal cells in the neighbourhood of the acantholytic foci. Satellitosis, phagocytosis of apoptotic material and apoptosis of dermal inflammatory cells were also observed. The special staining procedure, if compared with light microscopic observation of haematoxylin/eosin specimens, resulted in a reliable tool for identification of apoptotic cells in normal and lesional skin. Data on the presence or absence of apoptotic cells in the dermatopathies examined may cast a new light on the pathogenesis of these diseases.