Ergonomic problems of surgical lighting systems have been indicated by surgeons. However, the underlying causes are not clear. The aim of this study is to assess the problems in detail. Luminaire use during 46 h of surgery was observed and quantified. Furthermore, a questionnaire on perceived illumination of and usability problems with surgical luminaires was issued among OR-staff in 13 hospitals. The results showed that every 7.5 min a luminaire action (LA) takes place, intended to reposition the luminaire. Of these LAs, 74% was performed by surgeons and residents. For 64% of these LAs the surgical tasks of OR-staff were interrupted. The amount of LAs to obtain a well-lit wound, illumination level, shadows, and illumination of deep wounds were most frequently indicated lighting aspects needing improvement. Different kinematic aspects of the pendant system of the lights that influence usability were also mentioned: high forces for repositioning, ease of focusing and aiming, ease of moving, collisions of the luminaire, entangling of pendant arms, and maneuverability. Based on these results, conclusions regarding to improvement of surgical lighting systems are formulated. Focus for improvements should be on minimizing the need for repositioning the luminaire, and on minimizing the effort for repositioning.