OBJECTIVE: To assess whether a husband's Medicare transition leads to insurance disruptions for his wife that impact her perceived access to care, health care utilization, or health status. DATA SOURCES/STUDY SETTING: Respondents were married women under age 65 from the 2003-2005 round of the Wisconsin Longitudinal Study (N=655). STUDY DESIGN: Instrumental variable (IV) linear and IV-probit analyses provided unbiased estimates of the effect of an insurance disruption on study outcomes. The instrument was the husband's age: (1) women with husbands who transitioned to Medicare within the previous year (age 65-66); (2) women with husbands who did not transition (60<age<65). DATA COLLECTION/EXTRACTION METHODS: Respondents were surveyed via telephone and mail. PRINCIPAL FINDINGS: After adjustment, women who experienced an insurance disruption due to their husband's Medicare transition had a greater probability of experiencing a change in usual clinic/provider (71 percent), delaying filling or taking fewer medications than prescribed because of cost (75 percent), going to the emergency room (52 percent), and had lower average mental health scores than women who did not experience an insurance disruption. CONCLUSIONS: Despite consistent insurance coverage, the insurance disruption that accompanies a spouse's Medicare transition has adverse access and health care utilization consequences for women.