Despite recent attempts to improve classification and to provide data on pathogenic mechanisms, there is a paucity of information concerning the clinical aspects of bilateral renal dysplasia. Therefore, the clinical features and long-term prognosis of eight patients with bilateral renal dysplasia have been evaluated. Three important observations were made, namely (1) a large proportion of patients had an impairment of urinary concentration and acidification, (2) the clinical course was characterized by progressive renal deterioration in patients with bilateral involvement, and (3) four children with renal dysplasia had the clinical features of Laurence-Moon-Biedl syndrome.