This chapter argues that a critical task for newcomers entering work groups is learning the shared mental models that oldtimers possess. It suggests that whether newcomers joining intact groups acquire shared mental models during socialization depends on four factors-newcomers' qualities; newcomers' tactics; oldtimers' qualities; and oldtimers' tactics. The chapter explains several ways in which organizations might improve work groups' ability to transmit shared mental models to newcomers by bringing certain types of people into the groups and helping these people acquire the general and specific competencies they need to function effectively. Knowledge about the group as a whole might involve reasons why the group is unique, historical forces that shaped the group, and evaluations of the group's performance. Knowledge about members might involve characteristics of people who belong to the group, the kinds of relationships they have with one another, and appropriate ways of interpreting their behavior.