A quarterly, partial-equilibrium vector-autoregression model of the U.S. durum wheat and pasta markets was estimated and simulated under three trade-barrier changes that are of potential relevance for the current round of WTO agricultural negotiations: a rise in the U.S. market-clearing durum wheat quantity from increased imports; a policy- or tariff- reduction-induced decline in U.S. durum wheat price; and a tariff-induced rise in U.S. pasta product prices. In response to each shock, an array of quarterly dynamic response characteristics are examined: response reaction times, direction and pattern of quarterly responses, response durations, response multipliers, and strength of durum/pasta market interrelationships.