A study of the costs and economic effects of financing a national health insurance program by mandating that all employers provide insurance for their employees and dependents. Using data from a 1970 national health care survey to simulate the level of new premiums needed for the various amounts of mandated coverage, the authors examine the effects of these new employer costs on the U.S. economy. Conclusions are: (1) Employer premiums will increase between $5 and $21 billion. (2) Without offsetting subsidies, premium increases will cause a transitory decrease in employment. (3) Premium payments will eventually be reflected in lower taxable income for employees. Thus, potential tax revenues forgone, in 1975 dollars, could range from $1.3 to $5.9 billion. Combining this expenditure with existing uncollected taxes on employer insurance payments and the tax expenditures arising from itemized deductions of family-paid premiums, could result in a total tax expenditure of $8 to $12 billion, or about 4 to 6 percent of federal revenues from personal income and social security taxes. 53 pp. Bibliog.