Historically, doctors have not always acknowledged that they have an obligation to prevent suicide, partly because they shared the prevalent idea that most suicides were caused by moral crises, no concern of theirs—and indeed suicide was a criminal matter until quite recently; but more, perhaps, because a fatalism has characterized their attitudes to its prevention, even where the suicide was clearly suffering from mental illness. Yet two recent American studies have shown more than 90 per cent of suicides to be mentally ill before their death (17, 8); this finding and the familiar clinical observation that suicidal thoughts disappear when the illness is successfully treated provide a strong case for a medical policy of prevention.