This paper presents a study of collaboration in software design at a large software company. Ethnographic studies of development teams in the field are relatively rare, so this paper contributes to a small, but growing, body of knowledge about the collaborative activities involved in such design work. Five separate development groups were studied over a six-week period. The methodology included shadowing, interviews and communication event logging. A novel PDA-based application was used for real-time data collection. The results of the study indicate that designers communicate frequently, using a wide variety of communication and collaboration modalities. Designers prefer general-purpose tools to domain-specific applications. In support of communication, designers frequently change their physical location throughout the day. Finally, designers frequently change the ways in which they communicate, changing their communication modalities and styles.