For many evergreen plants in a temperate climate an increase in leaf nitrogen content is shown in winter. A high nitrogen content has been argued to serve as storage, photoprotection or maintaining photosynthesis at suboptimal conditions. One of the key arguments for storage of nitrogen is the role of Rubisco as storage protein being present at a low activation state (the proportion of active enzyme). This hypothesis, however, has not been tested. For 9 evergreen species in winter (February) and summer (September) we determined the Pmax and the initial slope of the A-Ci curve (IS) at 15°C in winter and 25°C in summer, the nitrogen and rubisco content per leaf area and the Rubisco activation state. The leaf nitrogen content in all species was on average 1.9 times higher in winter than in summer. The Rubisco content was significantly correlated to the leaf nitrogen content but not higher for some species in winter than in summer. In winter the Pmax for all species and the IS for 2 species was lower than in summer. The Rubisco activation state was high in winter and in summer for all species (average 0.86). Thus we conclude that Rubisco is not an inactive storage protein in winter and a high Rubisco content might contribute to photosynthesis at suboptimal conditions.