This study initially set out to measure the quality of the process for assigning patients to ANDRG's from medical record documentation to clinical coding and grouping as part of a larger direct patient costing study. It soon became apparent that this seemingly unimportant task was far more complex than was originally thought and generated information worthy of a report in its own right. The result is a document which recognises the need for considerable skill, knowledge and experience in dealing with a process which has a central and fundamental role in Casemix.