We report on a woman patient with organophosphate poisoning resulting from a psychotically motivated suicide attempt. After detoxification and during treatment with haloperidol and levomepromazine, she developed acute malignant neuroleptic syndrome (MNS) in which dyspnea requiring assisted ventilation was the main symptom. Discontinuation of the neuroleptics was enough to effect sufficient recovery. With this case report, we would first like to emphasize that MNS can evolve within a very short time into a severe and life-threatening situation requiring intensive medical care, and secondly to illustrate the implications of organophosphate poisoning and the consequent cholinesterase blocking far the differential diagnosis of MNS.