This paper delves into the debate on the proliferation of regional trade arrangements by focusing on bilateral agricultural trade data over the 1962-1995 period for countries that currently are members of NAFTA, Mercosur, the EU and APEC. Agricultural is chosen because it has historically been protected by developed and dis-protected by developing nations, while in the case of the EU, its Common Agricultural Policy was the major policy jointly managed and funded by member countries. We suggest that the literature has tended to focus on factors explaining the level of trade, and neglected factors affecting growth in trade. While neighborhood characteristics affect neighborhood trade, they also appear to affect the policy regimes of neighboring countries. The shift to more outward oriented regimes is thus likely to induce a dynamic in trade among neighboring countries requiring several years to stabilize. As neighborhood trade grows, it is natural to form trade arrangements so as to harmonize policies and to remove other barriers. If this is the case, then we should expect the growth in intra regional trade to exceed growth in extra-regional trade, and these patterns should occur before the formation of regional trade arrangements. Our results support this explanation.