Objective: Spouse caregivers have an increased risk of mental and physical illness during caregiving and widowhood. The authors sought to evaluate whether partners of an ill spouse have a higher likelihood of developing mental health or substance abuse ( MHSA) disorders than partners who have healthy spouses, accounting for both spousal illness and death. Methods: The authors used Medicare claims from 1993-2001 for 474,228 married couples. The authors used Cox models to determine the effect of spouse illness on partner MHSA diagnosis, controlling for demographic and clinical characteristics. Results: A wife's hospitalization increased the husband's risk of MHSA diagnosis by 1.29 ( 95% confidence interval [ CI]: 1.28-1.29) and his risk of depression by 1.49 ( 95% CI: 1.48-1.51). A husband's hospitalization increased the risk of a wife's MHSA diagnosis by 1.33 ( 95% CI: 1.32-1.33) and her risk of depression by 1.41 ( 95% CI: 1.39-1.42). A wife's death increased the risk of the husband's MHSA diagnosis by 1.12 ( 95% CI: 1.11-1.13) and increased his risk of depression by 1.49 ( 95% CI: 1.46-1.51). A husband's death increased the risk of the wife's MHSA diagnosis by 1.14 ( 95% CI: 1.14-1.15) and increased her risk of depression by 1.41 ( 95% CI: 1.39-1.42). Conclusion: Spouse hospitalizations and spouse death independently increase the risk for partner MHSA and depression diagnoses. These findings can identify which individuals are at greatest risk for emotional distress and should be targeted for interventions to relieve caregiver burden that can arise separately and additively from both spousal illness and death.