The medical expert system OnkoLeit supports the treating physician in the course of diagnostic and therapeutic decisions in oncological diseases. OnkoLeit offers assistance to the physician regarding the diagnosis and therapy of hematological oncological diseases (e.g. chronic myeloid leukemia, short CML or myelodysplastic syndrome, short MDS). The assistance functions are based on the NCCN guidelines (guidelines of the National Comprehensive Cancer Network) as well as expert knowledge of the Steinbeis Transfer Institute for Clinical Hematooncology, which further develops the expert system from a medical perspective.