A successful medical care for nephro-urologically ill children can only be guaranteed by efficient cooperation.--2. For more than 5 years there has been close collaboration in this field between the Department of Urology and the Department of Pediatrics in the Berlin-Friedrichshain Hospital.--3. In evaluating our experience some basic conditions are described which may serve as prerequisites for a successful cooperation.--4. Details of the content and organisation of cooperation between different clinical specialities vary according to local conditions.