Doctoral dissertation is devoted to integrated management systems, integrated quality management systems in the production companies of Latvia. Development and application of quality management standard ISO 9001, product standards, conformity assessment standards, industry specific quality management system standards have been analysed. Experience on application of ISO 9001, ISO 14001, OHSAS 18001 management systems standards in Latvian companies has been studied through empirical research. The Author elaborated initial and comprehensive self-assessment methodologies for integration degree evaluation of integrated management system. The both self-assessment methodologies were approbated in companies, which participated in empirical research. The sequence of integrated management system development and possibilities of integration are depicted in PDSA improvement cycle and by applying the logic of process model. Process improvement project has been implemented in one manufacturing company and it has been recognised that process improvements positively influence company’s integrated management system. Suggestions for improvement of Management system’s audit methodology are elaborated for integrated management system value-added auditing.