To identify caregivers at risk for adverse health effects associated with caregiving, the stress, coping, health and service use of 500 primary caregivers of patients with bipolar disorder were assessed at baseline, 6, and 12 months. K-means cluster analysis and ANOVA identified and characterized groups with differing baseline stress/coping profiles. Mixed effects models examined the effects of cluster, time, and covariates on health outcomes. Three groups were identified. Burdened caregivers had higher burden and avoidance coping levels, and lower mastery and social support than effective and stigmatized caregivers; stigmatized caregivers reported the highest perceived stigma (p < 0.05). Effective and stigmatized groups had better health outcomes and less service use than the burdened group over time; stigmatized caregivers had poorer selfcare than effective caregivers. Cluster analysis is a promising method for identifying subgroups of caregivers with different stress and coping profiles associated with different health-related outcomes. Copyright Caring for a relative with bipolar disorder poses both objective burdens such as increased expenditure of time and money, and emotional burdens such as worry, tension, and grief (Chakrabarti and Gill, 2002;Fadden et al., 1987;Perlick et al., 1999;Reinares and Vieta, 2004). Perlick et al. (2001) found that 93% of caregivers of patients with bipolar disorder reported a moderate or higher degree of caregiving strain when their relative was admitted to a psychiatric facility, and that 70% continued to report moderate or higher burden 15 months later.In addition to its impact on quality of life, caregiving strain has been associated with compromised health and mental health among caregivers of patients with major affective and other chronic mental disorders. For example, caregivers who report high levels of caregiving strain also report experiencing poorer general health and a higher number of chronic medical conditions relative to the general population (Gallagher and Mechanic, 1996), as well as increased primary care visits (Perlick et al., 2005), more sleep problems (Perlick et al., 2007), greater use of psychotropic drugs such as tranquilizers and antidepressants (Dyck et al., 1999), and increased risk of medical hospitalization (Gallagher and Mechanic, 1996). Finally, studies have shown that high levels of caregiving strain are associated with clinically significant levels of depressive symptoms (Coyne et al., 1987;Dyck et al., 1999;Struening et al., 1995).The causal links between caregiving strain, adverse health effects and increased service use have not been clearly elucidated. Studies have demonstrated an association between various forms of psychological stress and health complaints and/or use of primary care services (e.g., Katon, 1984;Olfson and Klerman, 1992;Salovey et al., 2000), and studies among caregivers have suggested that those who experience high levels of strain are low in coping self-efficacy or employ less effective coping strategies, whi...