Prochlorperazine (Compazine, PCZ) is a frequently used medication in the emergency department (ED). Akathisia and dystonia are known adverse reactions to the use of this medication, but their incidence in the ED has not been well studied. We conducted a prospective, descriptive study to evaluate the frequency of akathisia and dystonia in the ED from the use of IV or IM PCZ in patients with nausea/vomiting or headache. Two hundred-twenty nine patients (> or =18 years old) were enrolled and contacted within 2 weeks of ED discharge to access the incidence of these adverse reactions. After the use of PCZ in the ED, 16% of patients developed akathisia and 4% developed dystonia. Emergency physicians and our patients need to be aware of these potential adverse reactions to the use of PCZ in the ED.