We aimed to share the experience of the ISO/IEC 15189: 2007 accreditation process in a University Hospital's Medical Microbiology Laboratory before and after the assessment, and tried to seek answers to some questions in applying the standard. Our ISO 15189 accreditation process began in 2008 after having acquired JCI accreditation in 2007. The aim was to be the first accreditated university hospital laboratory in our country. The applied tests in bacteriology, mycology, parasitology, virology, immunology and molecular serology were accreditated. We completed the validation and verification procedures mostly applied to quantitative analyses. Regarding the external quality controls and the internal controls, the corrective actions provided us great control and self correction. We increased the rate of success in the quality controls. We encouraged our laboratory personnel to fill out a laboratory discrepancy form to control our process and to arrange training. During the course of 2009, 60 of the 85 forms were completed in the microbiology laboratory among the central laboratories. Statistical analyses were performed throughout a year and this information helped us in making improvements. The number of training hours in one year was found as 78 h and 30 min during the routine laboratory process. We should provide support in bringing quality to laboratories in our country. As a matter of fact, having our own external quality controls is believed to bring cost effectiveness in acquiring an accreditation process.