We present a blockmodel of the world system circa 1965 that is based on four types of international networks: trade flows,military intervention, diplomatic relations, and conjoint treaty memberships. We then report regression analysis of the effects of these structural positions on nations' economic growth (change in GNP per capita) from 1955 to 1970. Net of other plausible determinants, these effects are large in magnitude and entirely consistent with world-system/dependency theories. Further analyses reinforce the interpretation of these findings as the structural, accumulative advantage of location in the core over that in the periphery. Substantively, our results suggest that exogentic theories of economic growth are even more powerful than previous analyses have indicated. -Authors