Data exchange and interoperability between clinical information systems represent a crucial issue in the context of patient record data collection. An XML representation schema adapted to end-stage renal disease (ESRD) patients was developed and successfully tested against patient data in the dedicated Multi-Source Information System (MSIS) active file (more than 16,000 patient records). The ESRD-XML-Schema is organized into Schema subsets respecting the coherence of the clinical information and enriched with coherent data types. Tests are realized against XML-data files generated in conformity with the ESRD-XML Schema. Manual tests allowed the XML schema validation of the data format and content. Programmatic tests allowed the design of generic XML parsing routines, a portable object data model representation and the implementation of automatic data-exchange flows with the MSIS database system. The ESRD-XML-Schema represents a valid framework for data exchange and supports interoperability. Its modular design offers opportunity to simplify physicians' multiple tasks in order to privilege their clinical work.