The degree of market power exercised by fluid and manufactured processors in the U.S. dairy industry is estimated. Appelbaum's quantity-setting conjectural variation approach is cast into a switching regime framework to account for the two market regimes created by the existence of the dairy price support program: (a) government supported regime (market price is at the support price) and (b) market equilibrium regime (market price is above the support price). The model is also used to test whether government price intervention has a pro-competitive to anti-competitive influence on market conduct.