Herpetiform pemphigus is a rare variety of pemphigus vulgaris. Although the final diagnosis requires thorough clinical, histological and immunological investigations, there are simple examinations which may be carried out at once (such as assessment of blister stability, negative Nikolski's sign, predominance of eosinophils, spongiotic and non-acantholytic epidermal cells in the Tzanck smear). These ad hoc findings may help the practising dermatologist to tell herpetiform pemphigus from other blistering diseases. We discuss and evaluate the various diagnostic procedures regarding herpetiform pemphigus.