When anamnesis and clinical findings are suspicious of renal disease, laboratory examinations have to be performed, which are also necessary in evaluating the course of the disease. The first steps are urinalysis, blood sedimentation rate, red and white blood cell count, creatinine, supplemented by urea, electrolytes, acid-base-status, serum-protein with electrophoresis, cholesterol, triglycerides. For special questions beyond this immunological examinations are necessary (i.g. antibodies to basal-membrane, immunocomplexes). Among the renal function tests the concentration test is of some value. The endogenous clearance of creatinine can be determined with sufficient accuracy from the serum creatinine concentration alone by a formula.