This article describes the introduction of quality improvement actions in a public health organization. After ISO 17025 accreditation, which was legally mandated, was granted to the official control laboratory, the management decided to expand a quality policy in 2003, through a series of actions based on process analysis and proposals for improvement, further definition of standard operating procedures, exploration of users’ opinions, the creation of improvement groups, and external audits or certification. The organizational response to these initiatives was diverse. External audit or certification of services seems to be the most powerful tool for change. Costing studies showed that up to 75% of the total expenditure of the agency in 2010 was spent on public health services subject to external audit or certification.