Software development poses enormous cognitive, organizational, and managerial challenges. In this article, we focus on two of the most formidable of these challenges and on the promise of object-oriented (00) technology for addressing them. In particular, we analyze the claims made about 00 design (OOD) and (a) dissemination of domain knowledge and (b) communication and coordination. In order to address the validity of these claims, we conducted an in-depth observational study of OOD in an industrial setting as well as a series of interviews with experienced OOD practitioners. Compared to similar projects using traditional methods, our study found evidence in the OOD project for a reduced need for clarification in design discussions; differences in participation, in how meeting time is spent, and in the sequential order of design discussions; and a much greater tendency to ask why questions. We discuss the implications of these findings for tools, grain size of design units, interactions with clients, and organizing for OOD.