This paper provides a summary measure of the possible new commitments in the area of market access undertaken by the European Union and the United States, using the Trade Restrictiveness Index (TRI) as the tariff aggregator. Indicators such as the TRI, based on welfare theory, integrate economic behavioural assumptions within a balance of trade framework. We take the 2000 bound tariffs as the starting point and attempt to assess how much liberalisation in agriculture could be achieved in the European Union and the United States as a result of the present negotiations. We compute the index for agricultural commodity aggregates assuming a specific (Constant Elasticity of Substitution) functional form for import demand. The present levels of the TRI under the actual commitments of the Uruguay Round are computed and compared with three hypothetical cases: a repetition of the same set of commitments of the Uruguay Round, a uniform 36 percent reduction of each tariff, an harmonization formula based on the "sliding scale" scheme. This makes it possible to infer how reducing tariff dispersion would help improve market access in future trade agreements.