We examine the effects of employment-contingent health insurance (ECHI) on married women's labor supply following a health shock. First, we develop a theoretical framework that examines the effects of ECHI on the labor supply response to a health shock, which suggests that women with ECHI are less likely to reduce their labor supply in response to a health shock, relative to women with health insurance through their spouse's employer. Second, we empirically examine this relationship based on labor supply responses to breast cancer. We find that health shocks decrease labor supply to a greater extent among women insured by their spouse's policy than among women with health insurance through their own employer, suggesting that ECHI creates incentives to remain working when faced with a serious illness. Copyright © 2006 John Wiley & Sons, Ltd.