The potential impact of an ill child on other siblings in the family was examined by comparing 72 siblings of children with rheumatic disease with 60 siblings of healthy children from demographically matched families. Psychosomatic, behavioral, emotional, and social problems, as reported by both the parents and the siblings, were investigated. Although siblings of patients with rheumatic disease generally were functioning as well as siblings of healthy children, they reported having more allergies and asthma. A set of vulnerability and protective factors was tested as predictors of sibling functioning. Cohesive and expressive family environments in which mothers and patients with rheumatic disease were functioning adequately promoted better adaptation among the siblings.