[en] Recently we described a photosynthetic method for preparation of ₁₁C-labelled glucose using green algae. We have now developed the method further and included new techniques for purification and analysis of the obtained material. In the thin layer chromatographic analysis of the carbohydrates produced by the algae only one radioactive component was revealed. The systems used could not clearly separate glucose, fructose and mannose. The glucose content was determined using a specific method based on glucose oxidase whereas fructose was determined by an unspecific chemical procedure. The data thus obtained indicated that the algae produced glucose and fructose in a ratio of about 2:1. Mannose was not known to be present in the green algae used. GLC and HPLC have now other radioactive components to be present in the product. The ₁₁C-glucose produced by the algae and purified by HPLC has been used in positron emission tomography studies