This study was conducted to show that catatonia is a predisposing factor for neuroleptic malignant syndrome (NMS) and to review the nosological relationship between catatonia and NMS. Seventeen consecutive cases of NMS were analyzed prospectively with reference to clinical and investigative findings before and after exposure to a neuroleptic. The series comprised eight males and nine females, ranging in age from 18 years to 65 years. Prior to neuroleptic exposure, all patients exhibited features compatible with criteria for catatonia (mutism/excitement) according to the Diagnostic and Statistical Manual of Mental Disorders, Third Edition-Revised, (DSM-III-R). Following neuroleptic administration (single dose in nine cases), patients deteriorated into a febrile, rigid, and obtunded state accompanied by autonomic dysfunction and raised creatine phosphokinase levels. These features were consistent with a diagnosis of NMS. Neuroleptics were discontinued and supportive medical treatment instituted. Benzodiazepines were beneficial in eight cases in relieving stupor, but bromocriptine and dantrolene were generally ineffective. In all patients diagnosed with NMS in the authors' series, catatonia was an invariable prodromal state. It appears that the administration of a neuroleptic intensified the preexisting catatonic state and precipitated a malignant variant of the disorder, which is currently recognized as NMS. The authors, therefore, challenge the separate nosological status of NMS and catatonia and suggest that these syndromes are part of a unitary pathophysiological disorder.