The progression of qualified surgical nurses toward capable proficiency was examined in an ethnographic study during which 25 nurses, including 4 who transferred to other wards, were observed to determine whether social mediation affects the process of proficiency development. The nurses were observed for 18 months. Data were also gathered through invited observations of episodes of skilled behavior during which sequences of digital photographs of the nurse practitioners' actions were taken and knowledge maps linking scientific knowledge to nursing tasks and processes were sketched. After the observations, the nurse practitioners shared their reactions to the photographs and knowledge maps in post-observation interviews. The following were among the key findings: (1) the cognitive capacity for multiple representations of knowledge use enables engagement in the changing array of patient problems and the provision of solutions; (2) capable practitioners create and sustain their performance through strategies for emotional control that are transmitted directly to patients; (3) postqualifying newcomers are less able to project the practical implications of deliberative practice; and (4) collaborative working accelerates newcomer recognition of significant clinical signs during routine working, thereby giving newcomers access to distributed knowledge within settings characterized by a skill mix algorithm of 60% health care assistants to 40% qualified nurses. (Contains 18 references.) (MN)