Health insurance obtained through employment has enabled many workers to take advantage of the favorable tax treatment of employer contributions to these benefits. However, the full deductibility of such employer payments as a business expense and their exemption from income taxation are not available to self-employed owners of unincorporated businesses. We identify the sources of health insurance for the self employed and examine how this disparity in tax treatment is associated with health insurance status. Analyses of data from the 1987 National Medical Expenditure Survey reveal that the differential taxation of the unincorporated self employed is associated with lower rates of employment-related coverage for themselves and their workers.