In recent years, South America has witnessed a large increase in arms purchases. Nonetheless, there are important intraregional differences in terms of the allocation of resources for weapons acquisitions. How can we account for these disparities? Mainstream literature suggests that levels of arms importation depend on either the size of the defense budget or the perception of threat. In contrast, this article contends that the level of spending on arms is mainly determined by: (a) the expansive or nonexpansive nature of the strategic assessment of defense, (b) the available resources allocated by the defense budget, and (c) the level of political attention to defense issues. Thus, the aim of this article is to account for and assess the determinants of the different levels of arms importation in South America from 2000 to 2011.