A simple stochastic model of the firm is constructed in which a dynamic monopolist who maximizes a discounted profits stream subject to labor adjustment costs and given factor prices sets output price as a distributed lag of past wages and input prices. If the observed relation of wages and prices in manufacturing arises solely from this behavior then wages and input prices are exogenous with respect to output prices. In tests using quarterly and monthly series for the straight time wage, an index of raw materials prices and the wholesale price index for manufacturing and its durable and nondurable subsectors this hypothesis cannot be refuted for the period 1955:1 to 1971:11. During the period 1926:1 to 1940:11, however, symmetrically opposite behavior is observed manufacturing wholesale prices are exogenous with respect to the wage rate, a relation which can arise if dynamically monopsonistic firms compete in product markets. Neither structural relation has withstood direct wage and price controls.