In a 32-year old woman under ajmaline therapy for cardiac arrhythmia, a sudden episode of acute haemolytic anaemia and renal failure led to the identification of a potent agglutinating, haemolysing and lymphocytotoxic antibody specific to ajmaline and cross-reacting with quinine and quinidine. The immunological features of the antibody and the pathophysiological mechanism of blood cell destruction are presented, together with a brief synopsis of drugs incriminated so far in the induction of specific antibody formation and immune haemolytic anaemia.