To enhance surgical systems we need to manage the performance of the teams that comprise them. To do this we must measure the properties and processes of teams and account for the demands and conditions of their work. Recent research shows that observation is a potentially valuable method of measurement, but its potential application in surgery remains unclear. In this study of laparoscopic cholecystectomy, an observer applied observational measures of teamwork in the operating theatre and recorded intra-operative interference from observed distraction and interruption. Results showed that it was feasible to observe a broad scope of teamwork and to reveal the frequency and source of work interference. However, the measures were necessarily selective and so limited in their analysis of the conditions and events that might interfere with the collective work in surgery. Such measures may however prove useful when applied in conjunction with other methods of measurement and utilised as performance feedback data.