Psychotropic drugs frequently cause agranulocytosis. It is therefore important that patients on these drugs who develop symptoms or signs of infection should have a full blood count performed, and if the neutrophil count is reduced, prompt withdrawal of the drug and, if necessary, immediate supportive care should be given to reduce the incidence of mortality. Once the patient has recovered, investigations can be performed to confirm the diagnosis and incriminate the responsible drug. It is imperative, in order that these tests may be performed, that serum samples are taken at the time of diagnosis of the neutropenic episode, throughout its course and during the recovery period.