São Luiz was granted in 2007 the most important domestic certificate of hospital accreditation, the ONA. The ONA assessment system is regarded as the most appropriate for leading health organizations in Brazil, and through such achievement, São Luiz assured quality in the support and safety of patients and professionals, thus meeting consistent criteria and goals which fit the Brazilian scenario and the ongoing improvement of services provided by São Luiz. The study was carried out by DNV (Det Norske Veritas).