This study investigates the development of relational intimacy in computer-mediated communication (CMC) by comparing it to face-to-face (FTF) interaction in a laboratory experiment. It also examines the influence of task type, gender, and group composition. Using a mixed-model factorial design, zero-history participants (n = .48) were grouped into dyads and asked to cooperate on low- and high-equivocality tasks over a series of three meetings conducted on three consecutive days. Results indicate that relational intimacy increased over time, but a significant interaction with medium and subsequent analyses reveal that this was only true for the CMC condition. Task type also interacted with time, but it did not have a significant effect on relational intimacy, nor did it interact with medium. Similarly, there was no main effect for either participant gender or group composition, nor did these factors interact with medium. The findings provide some support for the hyperpersonal communication model (Walther, 1996), which predicts that, under certain circumstances, interpersonal relationships can develop in CMC to a greater extent than they can in FTF interactions.