Rubisco (Ribulose-1.5-bisphosphate carboxylase/oxygenase) from spinach was purified to homogeneity in one step by gel filtration. This enzyme is suitable for the generation of a specific antibody in rabbits. The enzyme concentration in spinach leaves amounted to 40 % of the total soluble protein. The specific antibody shows cross reaction with crude extracts from leaves of other higher plants. The enzymes subunits could be separated by denaturing preparative SDS gel electrophoresis.