Neutropenia and agranulocytosis are among the most serious and feared adverse effects of antipsychotic drugs. In affected patients there is a risk of both infection and exacerbation of the underlying psychotic disorder, because neutropenia and agranulocytosis often require discontinuation of the antipsychotic drug therapy. The cause is most likely multifactorial. Whenever patients treated with antipsychotic drugs experience fever or other symptoms of infection, neutropenia should be considered as a differential diagnosis.