Recent protectionism by the United States has principally taken the form of negotiated barriers to trade, such as voluntary export restraints. These barriers tend to evolve over time and to display three patterns, which we label institutionalized, temporary, and sporadic protectionism. Cartel theory and studies of the politics of protection suggest that the dynamics of negotiated protectionism will depend on three variables: the barriers to entry into an industry, the size of the domestic industry, and the exit barriers for domestic firms. Low barriers to entry will lead to institutionalized protectionism when the domestic industry is large and exit difficult; temporary protectionism results when the domestic industry is small and exit easy; and sporadic protectionism is likely when barriers to entry are high. Brief studies of U.S. protectionism in textiles and apparel, steel, footwear, televisions, and automobiles illustrate the value of this framework.