Öz This paper examines the impact of total quality management TQM practices and ISO 9000 quality assurance certificate on hospital performance. The study survey was conducted in Istanbul at random selected sample of 60 private hospitals. The hospitals were categorized as follows: 1 non-adopters, 2 TQM adopters, and 3 the ones certified their TQM practices with ISO 9000. The results are: having ISO 9000 certificate was found related to plant size; both the TQM adopters and the certified group target high income social class; and those two groups of hospitals also revealed higher performance. Although ISO 9000 certificate, in particular, provides competitive advantage to hospitals, operational efficiency, however, cannot be predicted by either TQM adoption or ISO 9000 certificate.