Informal patient groups on an open psychiatric ward are identified and described by observational and sociometric techniques. The structures and functions of these groups are studied in relationship to those of more formal patient groups. Theleadership cliquefunctioned as a governing, staff-value supporting, and quasi-socializing agency, Thedissident cliquepermitted withdrawal of about-to-be-discharged patients from institutional values but also undermined staff values. Theformal therapy groupstended to be the focus of friendship-choices, especially during periods of unstable community norms.Friendship groupsprovided a protective environment in which the development of a favorable and reality-oriented self-image may occur.