To the Editor: Dr. Matejkowski et al. are correct that he and his coauthors did not claim in their study that individuals with severe and untreated psychiatric disorders "are responsible for approximately 10% of the homicides in the United States." That was my conclusion based on their data and on two previous studies. Among 518 offenders convicted of murder in Indiana, Matejkowski et al. said that 27 had schizophrenia, 14 had mania or bipolar disorder, 14 had another psychiatric disorder, and 58 had major depression (1). The authors themselves claimed that 95 of them, or 19%, had "severe mental illness." Among those for whom a treatment history was known, 43% had never been treated or had been treated only once.