A study of numbers and types of crimes in 704 mental patients committed to Khanka state mental hospital from 1967 till 1977 was made.Out of these 395 were found to be major crimes, and 297 were found to be minor ones. The commonest diagnostic category involved was that of schizophrenia followed by manic depressive illness. The higher incidence of schizophrenia as a source of a dangerousness amongst the mentally disturbed is going in line with the wider prevalence of that disorder in the sample provided and in the population at large.