L-Asparaginase is a protein produced by Escherichia coli and exists in two types, A and B. Only type B shows a specific antitumor activity to acute lymphatic leukemia. A new recombinant E. coli BL21Gold (DE3) pET11a-ansB was used to produce L-asparaginase B in higher quantities. To enhance the purity and preserve the activity of L-asparaginase B, crystallization is a promising process. Based on available patents, first experiments on L-asparaginase B crystallization were performed. Recombinant L-asparaginase B was successfully and reproducibly crystallized in two modifications. Up to now, it is not clear in which respect these two modifications of crystalline L-asparaginase B differ. It is part of the current study to investigate the nature of protein crystals in detail. The investigations on lysozyme crystals are well in agreement with the literature.