Within the frame of hospital quality control programme, the authors have investigated since 1997 the medical documentation concerning in-patients of St. Stephen Hospital Budapest. An assessment form of 26 items related to main elements of medical documentation has been created for the study. Choosing of both order of departments' succession and cases to be investigated took place at random. Evaluation was performed at a scala of 0-3 points, by a five-membered work-group; all members first carried out the qualifications independently of each other, and then they formed the final opinion together at common sessions. Investigation of 204 "first round" cases proved the feasibility of the applied method. As it turned out from the results, the quality of documentation showed statistically significant differences between departments of the hospital and the average standard of documentation could not be declared as satisfying at the period of basic survey. Deficiencies of documentation especially in respect of case history, disease course, personal data and informed consent have been found. On the other hand, registration of status on admission and final report got a relatively high average score-number. The authors call attention to the importance of ordinary control of medical documentation.