Power is a central aspect of nursing, especially in telephone-advice nursing, where nurses assess callers' medical problems and decide what measures that need to be taken. This article presents a framework for understanding how power operates in social interaction between nurses and callers in telephone-advice nursing in primary care in Sweden. Power is analysed as the result of nurses and callers being oriented to five social structures that are relevant to their actions in this context, namely the organization of telephone-advice nursing, the social stock of medical knowledge, the professional division of labour between nurses and doctors, structures of social interaction and structures of emotions. While structural constraints govern some actions to a high degree, calls take place in an organizational free room that give nurses more leeway for acting more creatively. The discussion focuses on the introduction of new technologies of control, for instance computerized decision support systems and audio recording of calls, and on how they reduce the free room. Empirical data consist of 276 audio-recorded telephone calls to 13 nurses at six primary-care centres and of qualitative interviews with 18 nurses.