This paper reports on findings from an evaluation of insurance coverage expansions in California, Massachusetts, New Jersey and Wisconsin. Overall, parents in Wisconsin and parents and childless adults in Massachusetts experienced the largest expansions in public coverage, with little offsetting reductions in private coverage. By contrast, coverage expansions for parents in California and New Jersey led to increased enrollment in publicly sponsored programs, but often with a corresponding drop in private coverage. With constraints on resources curtailing state coverage efforts, the study finds evidence that cuts in public coverage will likely put more adults at risk of becoming uninsured. (Health Affairs Web Exclusive, January 17, 2006)