Nine patients with pemphigus vulgaris and one with pemphigus vegetans were studied. All ten patients had oral lesions, five of them skin involvement as well. The patients were followed up for variable periods at different intervals. At each visit, their clinical condition was assessed as mild, moderate, severe or remissive. At examinations, oral light microscopical smears and blood samples for indirect immunofluorescence were taken. From one patient with pemphigus vulgaris, smears from skin blister fluid were also studied. The highest intercellular antibody titers were found in severely affected patients, and those at the mild stage of the disease usually gave low or negative titers. A correlation between the number of acantholytic cells in smears and the clinical condition of the patient was usually found: improvement of the clinical state was followed by decreased numbers of acantholytic cells.Acantholytic cells were rounded or ovoid, having an enlarged, hyperchromatic, centrally or eccentrally situated nucleus. The cytoplasm was usually eosinophilic.Neutrophilic polymorphonuclear leucocyte/acantholytic cell rosettes were sometimes seen in the smears, as well as eosinophil/acantholytic cell rosettes. Variable numbers of leucocytes (from 3 to 11) were seen surrounding the acantholytic cell.Both binucleated epithelial and acantholytic cells and multinucleated giant cells were found in the smears. Multinucleated giant cells were sometimes seen engulfing cells resembling acantholytic cells.