The understanding how complement relates to glomerular diseases has evolved considerably during the last years. Substantial evidence has accumulated that explain how a defective or deregulated complement system results in kidney diseases. The combination and close interaction of basic research with clinical medicine has demonstrated an important role of complement effector and regulatory proteins in pathological settings of the kidney. A large panel of distinct human kidney diseases such as hemolytic uremic syndrome (HUS), membrano proliferative glomerulonephritis (MPGN), systemic lupus erythematosus (SLE) and in ischemic reperfusions injury and transplantation are caused by defective complement control. Genetic analyses have identified mutations in complement regulators that are associated with these diseases. Mutations have been identified in the fluid phase alternative pathway regulator Factor H and the membrane regulator Membrane Cofactor Protein MCP (CD46). The functional characterization of the mutant proteins allows to define the pathophysiological events on a molecular level. These new concepts and data on disease mechanisms already allowed to establish new diagnostic and novel promising therapeutic approaches for several human kidney diseases.