One important innovation in information and communication technology developed over the past decade was organizational rather than merely technological. Open source production is remarkable because it converts a private commodity (typically software) into a public good. A number of studies examine the factors motivating contributions to open source production goods, but we argue it is important to understand the causes of high quality contributions to such goods. In this paper, we analyze quality in the open source online encyclopedia Wikipedia. We find that, for users who create an online persona through a registered user name, the quality of contributions increases as the number of contributions increase, consistent with the idea of experts motivated by reputation and committed to the Wikipedia community. Unexpectedly, however, we find the highest quality contributions come from the vast numbers of anonymous "Good Samaritans" who contribute infrequently. Our findings that Good Samaritans as well as committed "Zealots" contribute high quality content to Wikipedia suggest that open source production is remarkable as much for its organizational as its technological innovation that enables vast numbers of anonymous one-time contributors to create high quality, essentially public goods. Word count: 188 Explaining Quality in Internet Collective Goods: Zealots and Good Samaritans in the Case of Wikipedia I. Introduction Of the significant advances in information and communication technology over the past decade, some important innovations were organizational rather than technological (Neff and Stark 2003; O'Mahony 2003). One of the most important organizational innovations is the emergence of open source production, which involves the free and open creation, alteration and distribution of goods, typically software, via the contributions from vast numbers of widely distributed and uncoordinated actors (Lakhani and Wolf 2005; Open Source Initiative 2005). Essentially, open source production is remarkable because it converts a private commodity (software) into essentially a public good (Kollock 1999; Kogut and Metiu 2001; O'Mahony 2003). 1 Indeed, advocates of open source software often describe it as a movement rather than a production process because it appears to give rise to the strong commitment and group identity often found in social movements (Raymond 2001; Stallman 1999; Torvalds and Diamond 2001). Given the inherent social dilemma in producing public goods (Olson 1965; Hardin 1968; Kollock 1998), open source production would seem to be based on a problematic and inefficient model. Some argue, however, that open source production can be not only efficient (Kogut and Metiu 2001), but even superior (e.g., von Hippel 2001; Weber 2005) to other forms of production. The central questions for understanding open source production are who contributes to open source goods, and why? Despite much hype that a distributed community of anonymous participants create high quality goods via open source production, early studies ...