BACKGROUND: External supervision of primary healthcare facilities in low- and middle-income countries often has a managerial main purpose in which the role of support for professional development is unclear. AIM: To explore how Rwandan primary healthcare supervisors and providers (supervisees) perceive evaluative and formative functions of external supervision. DESIGN: Qualitative, exploratory study. DATA: Focus group discussions: three with supervisors, three with providers, and one mixed (n = 31). Findings were discussed with individual and groups of supervisors and providers. RESULTS: Evaluative activities occupied providers' understanding of supervision, including checking, correcting, marking and performance-based financing. These were presented as sources of motivation, that in self-determination theory indicate introjected regulation. Supervisors preferred to highlight their role in formative supervision, which may mask their own and providers' uncontested accounts that systematic performance evaluations predominated supervisors' work. Providers strongly requested larger focus on formative and supportive functions, voiced as well by most supervisors. Impact of performance evaluation on motivation and professional development is discussed. CONCLUSION: While external supervisors intended to support providers' professional development, our findings indicate serious problems with this in a context of frequent evaluations and performance marking. Separating the role of supporter and evaluator does not appear as the simple solution. If external supervision is to improve health care services, it is essential that supervisors and health centre managers are competent to support providers in a way that transparently accounts for various performance pressures. This includes delivery of proper formative supervision with useful feedback, maintaining an effective supervisory relationship, as well as ensuring providers are aware of the purpose and content of evaluative and formative supervision functions.