Emotional and physical relationships among copatients on a short-term psychiatric unit were assessed in a two-year prospective study. Sixty-four relationships involving 102 patients were reported; the incidence rate was estimated at 10.7 percent. Thirtythree percent of the relationships were characterized as emotional, 9 percent as physical, and 58 percent as both. Patients involved in the relationships tended to be young and unmarried and to have a diagnosis of eating disorder, personality disorder, or bipolar disorder. Although most of the relationships were reciprocal, half were judged to be destructive and to create management problems. Staff discussed the relationship with the patients when it was considered destructive or exploitative but ignored relationships felt to be positive and healthy. The authors urge further studies of such relationships to help clarify patient management issues.