One of the most interesting aspects of the pathogenesis of the allergic and pseudo-allergic reactions to drugs is the one concerning the possible roles of genetic factors, in general, and the relationship with atopy, in particular. We decided to study the correlation between the serum level of total IgE, the personal and familial history of atopy, and the allergologic tests (skin test, PRIST, RAST, etc) for one or more drugs taken by 465 patients with personal history of allergic reactions. From the data, we observed that the average amount of total IgE lies within the norm, 125.4 KU/L (+/- 209.2), without any significant difference between the allergic (132 KU/L) and the pseudo-allergic (121.8 KU/L) patients. The IgE levels tend to be higher in that part of the tested population which presented a circumstantial atopic status (11.8%) and they are not influenced by an allergic or pseudo-allergic reaction to drugs. According to these results, the relationship between drug hypersensitivity and atopy needs further investigation.