This study contains estimates of wage equations for white male union and nonunion employees. The authors find that nonunion wages are generally more responsive than union wages to individuals' education and experience and to regional price-level variation. Despite those differences, however, estimates of union-nonunion wage differentials based on these separate equations do not differ greatly from a differential obtained from a union dummy variable in an equation based on combined union and nonunion observations. Union-nonunion differentials vary widely across occupational groups and are generally larger in the lower skilled and more highly unionized occupations. The results for manufacturing, for which additional industry data are available, indicate a negative impact of high concentration ratios on the wages of all workers and a greater impact of establishment size on nonunion than on union wages. Data were drawn from the May 1973 Current Population Survey.