The Authors performed ona group a patients suffering from drug exanthema a thorough clinico-anamnestic and allergo-immunological investigation (skin reactions, patch-tests, Prausnitz-Küstner passive transport, in vitro lymphocyte blastization, total serum IgE radioimmunoassay). The results obtained do not support an immunoallergical pathogenesis of this syndrome. The possible alternative hypotheses and the future perspectives of study are discussed.