We analyse the consequences on agricultural markets of enlargement of the European Union (EU) to include the Czech Republic, Hungary, and Poland. We produce a market outlook up to 2010 for two enlargement scenarios assuming different policy restrictions on grain and dairy production in the acceding countries. Accession of the three Central and Eastern European countries (CEECs) leads to a permanent but moderate decrease in EU prices for most commodities. In the three acceding CEECs, domestic prices increase drastically, final consumption of agricultural products decreases in most instances, while production increases. Higher domestic prices in the CEECs reduce exports of most commodities to non-union countries. Consequently, excess supplies are placed in stocks or exported to the original 15 member countries. Supply management mechanisms in the dairy and grain sectors would reduce the build-up of surpluses in the new member states, but limit their ability to take advantage of the expanded market. Accession of the three CEECs would increase the CAP budget over its proposed maximum if area payments are extended to incoming crop producers.