• Family history of appendicitis was studied in 135 children with histologic confirmation of acute appendicitis and in 212 control children without appendicitis, matched by age, sex, and admission date. Parents of patients with appendicitis were approximately 10% more likely than parents of control children to have a positive history of this disease, a difference that could have easily arisen by chance. In contrast, seven patients with appendicitis had siblings with a history of appendicitis, whereas only 0.64 would have been expected on the basis of the proportion among the control group. A significant positive trend was also noted between the proportion of family members with a history of appendicitis and risk for this disease in children. These results indicate some familial tendency for appendicitis, although not to the extent suggested by previous studies.