The drug-induced blood dyscrasias are caused by the interaction of different drugs with the hematopoietic cells through specific receptors. Other pathophysiologic mechanisms may be by direct toxicity to bone marrow or peripheral cells, hypersensitivity, immunological defects secondary to viral infections, mixed or unknown mechanisms. The first associations were described in the thirties. Drugs with higher relative risk of agranulocytosis or aplastic anemia are antithyroid, carbamazepine, sulfonylurea, indomethacin and piroxicam among others. The report of a clinical case in an adult patient who after the administration of vancomycin presented agranulocytosis with resolution of the clinical picture after its suspension, is presented. (Acta Med Colomb 2014; 39: 279-282)