summary The pdss is a potential side-effect of the intramuscular injection of olanzapine pamoate. We saw the typical symptoms develop in a 46-year-old man 4 hours after the injection. The syndrome is caused by a toxic concentration of olanzapine, and is possibly the result of the direct injection of the substance in the bloodstream. The most important measures that can be taken to prevent such an emergency are: a careful injection procedure, a 3-hour observation period following the injection and good counselling of the patient and his family. The treatment is conservative.