1. Defects in transport systems of renal tubules are caused by partial tubular dysfunction without preceeding renal disease. There is a well delineated disturbance for the reabsorption of certain substances. Most commonly the defects in transport of renal tubules are genetically determined. 2. Symptoms are due to secondary renal dysfunction and nephrolithiasis or extrarenal disturbances. Primary defects in transport systems of renal tubules, therefore, should be considered for differential diagnosis. 3. There is no therapy for the genetic defect. However, in case of early detection a symptomatic treatment is mandatory. This prevents clinical symptoms and sequelae.