The study used information from 233 reports published in English and French between 1940 and 2000. The analysis focused on four hypotheses presented by researchers in recent years. Results indicated adults who murdered their parents more often had an older brother, older sister, or both than were juveniles who killed their parents. Those juveniles were more often first-born or single children. However, no differences existed in the number of siblings of adults and juveniles who killed their biological fathers and those who killed their biological mothers. Results also revealed that biological mothers were more often killed by males who were the only male child than were the murdered biological fathers. Tables, notes, and 25 references