OBJECTIVE This report identifies neuroleptic malignant syndrome (NMS) occurring on a steady state dosage of clozapine monotherapy. METHODS An outpatient presented with a recent history of stiffness and soreness of his legs, dizziness, polydipsia, polyuria, abdominal and chest pains. After admission to a general hospital, further symptomatology was identified including: pallor, diaphoresis, nausea, confusion, agitation, decrease in normal reflexes, minimally reactive pupils and rigid limbs. METHODS Intravenous (I/V) diazepam was administered but failed to decrease the agitation and confusion. He was sedated with the administered of I/V droperadol, intubated and placed on a ventilator with circulatory supports for 4 days. RESULTS On day five he was extubated and transfered to a medical ward. All laboratory values had returned to normal values by this time. The patient was subsequently discharged. CONCLUSIONS Neuroleptic malignant syndrome can occur at any stage of clozapine treatment, and the patient can be rechallenged after such an episode. This person was rechallenged and after 6 months of treatment has suffered no further recurrence of NMS.