Seventy-four adult siblings of individuals with a schizophrenia spectrum disorder were interviewed by telephone regarding the effects that having a sibling with a chronic mental illness has had on them. Specifically, this study examined the effects that problem-focused coping, emotion-focused coping, perceived social support, premorbid interpersonal closeness with the mentally ill sibling, subjective burden, time since onset of the illness, frequency of contact with the mentally ill sibling, perceived controllability of the consequences of events related to the mentally ill sibling, and perceived severity of the illness had on well siblings' depression, self-concept, relationships and functioning in daily roles. Use of problem-focused coping and use of emotion-focused coping were significantly negatively correlated with impact on relationships. Perceived social support was significantly negatively correlated with depression and significantly positively correlated with self-concept. Frequency of contact with the mentally ill sibling, subjective burden of the illness on the subject, and perceived severity of the illness were significantly positively correlated with impact on role functioning of the subject. There were significant interactions between both the use of coping behaviors and frequency of contact in the prediction of psychological distress (a combination of depression and self-concept), and impact on relationships. When use of coping was low, frequency of contact with the mentally ill sibling was significantly positively correlated with psychological distress and impact on relationships; when use of coping was high, frequency of contact with the mentally ill sibling was significantly negatively correlated with psychological distress and impact on relationships. There was a significant interaction between the use of coping behaviors and perceived severity of the illness in the prediction of depression. When use of coping was low, perceived severity was significantly positively correlated with depression; when use of coping was high, perceived severity was significantly negatively correlated with depression. These findings have several strong implications for clinical work with siblings of the mentally ill. These include psychoeducational interventions that focus on the use of effective coping strategies, alleviating burden, and reframing the severity of the illness. Additionally, social support interventions may be helpful in alleviating the adverse effects of sibling mental illness.