This study examines the market structure-conduct-performance relationship for 48 four-digit SIC Food and Tobacco Processing Industries during the 1970s, 1980s and 1990s. The simultaneous-equation analyses are used to explore the relationship among price-cost margin (PCM), market concentration, advertising outlay, and various control variables. With an intertemporal setting, our findings provide evidence of structural changes over time in the U.S. food manufacturing sector and support some of the conventional SCP wisdoms, but challenge others.