This study examines the role of perceived interactivity and other marketing tactics in relationship building with customers in the online retail environment by applying a relationship investment model adapted from De Wulf, Odekerken-Schröder, and Iacobucci (2001). A proposed structure model was tested with data collected from an online survey of 571 respondents. In the model, three subdimensions of perceived interactivity and three marketing tactic variables were incorporated as the antecedents of perceived relationship investment that subsequently influenced perceived relationship quality and behavioral loyalty. Results suggest that two marketing tactics—direct mail (e-mail) and tangible rewards—and two dimensions of perceived interactivity—synchronicity and two-way communication—play as significant antecedents for the relationshipbuilding process of online retail brands. In addition, the findings confirm the relationships among perceived relationship investment, relationship quality, and behavioral loyalty, which indicates that the fundamental process of relationship building remains similar in the online environment. Reflecting the unique nature of the online retail environment, the model also clarifies the roles of interactivity as well as traditional relationship investment strategies in facilitating online retailers' relationship building with customers. © 2008 Wiley Periodicals, Inc.