Anti-drug serum human IgE can be detected by passive sensitization "in vitro" of monkey lung tissue. This technique gives reproducible results which are not quantitative. It is sensible; there are no false positive results and the number of false negative results has been strongly decreased. This technique is really an anaphylaxis and IgE only are detected. The results concern the study of 215 patients which possible drug allergy. The most frequent drugs come from groups of penicillins, sulfonamides, salicylates and malonylurea derivates. In 54% of cases, anti-drug IgE have been detected.