The national and international rates of homicide and homicide-suicide (dyadic death) have been studied by examination of the available literature. The rates of homicide-suicide episodes between different countries showed considerable variation, though not as great as overall homicide rates. Despite the variation the features of the episodes were similar, with a man usually killing his spouse and/or children with a firearm. The commonest motive for killing is jealousy and/or revenge, often as the result of a breakdown in the spousal relationship.