The purpose of this study was to examine the effectiveness of water and sanitation service delivery in resource-limited settings using two different social theories (modernization and world system). Understanding that barriers to effectiveness are rooted in global structures that tend to present at local levels helps redefine the problem leading to comprehensive policies and practices. The guiding research questions included an identification of an effectiveness gap in services delivered in developed countries compared to those in developing countries. This study included a survey of water and sanitation professionals gauging their opinions on trends within the sector. Survey respondents demonstrated that the sector tends to align with localized (i.e. modernist) approaches. This may explain the perpetuation of differential patterns in water and sanitation access and associated diseases and deaths in developing countries. Through a case study of Partners In Health (PIH), a medical-oriented non-governmental organization used as a proxy for water and sanitation organizations, this work illustrated why personal and organizational philosophies and perspectives influence how we organize and act. It concludes with a discussion of engineering decision making through the lenses offered by modernization and world system theories; presents an organizational structure that allows organizations to overcome theoretical and geographic boundaries; and offers a set of recommendations learned from PIH and those the sector does well. This research shows how water and sanitation organizations, practices, and policies that consider local and global forces are more effective at delivering services in developing countries than those focusing solely on local forces. / Ph. D.