Much research in sociology and labor economics studies proxies for productivity; consequently, little is known about the relationship between personal contacts and worker performance. This study addresses, for the first time, the role of referral contacts on workers' performance. Using employees' hiring and performance data in a call center, the author examines the performance implications over time of hiring new workers via employee referrals. When assessing whether referrals are more productive than nonreferrals, the author also considers the relationship between employee productivity and turnover. This study finds that referrals are initially more productive than nonreferrals, but longitudinal analyses emphasize posthire social processes among socially connected employees. This article demonstrates that the effect of referral ties continues beyond the hiring process, having long-term effects on employee attachment to the firm and on performance.For decades, we have seen a stream of theoretical and empirical studies in economic sociology and labor economics examining how recruitment sources relate to employees' outcomes such as turnover and tenure, starting wages, and wage growth (for a detailed review of these studies, see 1 I am grateful for the financial support provided by the Social Sciences Research Council (Program of the Corporation as a Social Institution). I have benefited enormously from the extensive and detailed comments of Roberto M. Ferná ndez, Mark Granovetter, and John W. Meyer. I thank Robert Freeland, Ezra Zuckerman, and Dick Scott for their wonderful suggestions on earlier versions of this paper. I also thank my colleagues in the Management Department at Wharton, especially Mauro F. Guillén, Anne-Marie Knott, Lori Rosenkopf, Nancy Rothbard, Christophe Van den Bulte, Steffanie Wilk, and Mark Zbaracki, and all the attendees of the M-square seminar for their comments on earlier drafts. I am also extremely thankful to the entire Ferná ndez family for all their love and support. Direct correspondence to Emilio J.