Levomepromazine (LMP) unexpectedly improved 16 of 23 chronic treatment-resistant schizophrenic patients who were hospitalized in most cases for at least 2 years and who manifested positive symptoms, irritability and, in many cases, restlessness, hostility, uncooperativeness, poor concentration and aggressive behavior. Improvement led to discharge in 7 (6 to a foster home), placement on a waiting list for a foster home in 4 and improved behavior and autonomy in 5 patients. Five subjects developed seizures and 1 agranulocytosis. Whether improvement with LMP is caused by unique antischizophrenic properties or by diminished liability to induce side effects such as akathisia, a formal controlled study of LMP in treatment-resistant schizophrenia is merited.