Since 1988 the MDK (Medical Service of the health insurances) in Lower Saxony has frequently been asked to clinically assess potential malpractice cases according to the German social law (Sect. 66 SGB V and Sect. 116 SGB X). In Lower Saxony this amounts to more than 2,000 assessments per year. By far the most treatment errors as compared to all other medical disciplines are seen in the surgical field. Surprisingly, the highest rate of errors is found in diagnostic and case management rather than in actual surgical therapy. With about 20% the complaint rate with the MDK of Lower Saxony has largely remained unchanged during the last years.