The basophil activation test (BAT) has been suggested as a complementary method for diagnosing drug allergies. The aim of this study was to evaluate the clinical utility of this test in patients with drug-induced anaphylaxis. In total, 19 patients, all of whom had a history of moderate to severe anaphylaxis, were enrolled. None of the causative drugs had available in vitro tests or reliable skin tests; these drugs included, among others, first and second-generation cephalosporins, H2 blockers, and muscle relaxants. The BAT yielded positive results in 57.9% of the cases, which was similar those results of skin prick and intradermal tests (42.1% and 57.9%, respectively). When basophils were double labelled with CD63 and CD203c, both of which are basophil activation markers, the positive rate was increased from 57.9% to 73.7%. Therefore, the results of this study confirm that the BAT is a quick, reliable, and safe diagnostic tool for patients with drug-induced anaphylaxis.