Family environment has been shown to be one of the factors related to the presence of eating disorders among young-adult females. Clinical experience and theories about eating disorders postulate that implicit family rules are an intricate part of family process that may have a great effect on the creation and maintenance of such problems. This study compared implicit family process rules (specifically rules pertaining to kindness; expressiveness and connection; constraining thoughts, feelings, and self; inappropriate caretaking; and monitoring) in families with a young-adult female diagnosed with an eating disorder--either anorexia nervosa, bulimia nervosa, or eating disorder not otherwise specified--and families with a young-adult female without an eating disorder diagnosis. One hundred two families (51 eating disordered and 51 comparison) participated in the study. Mothers, fathers, young-adult female children, and siblings completed the Family Implicit Rules Profile (Harper, Stoll, & Larson, 2007). Results indicated that eating-disordered families are governed by a greater proportion of constraining family rules than are non-eating-disordered families. Additionally, eating-disordered youth reported a lower proportion of facilitative family rules and a higher proportion of constraining family rules than did parents and siblings. Theoretical, research, and clinical implications are discussed. (Contains 1 table.)