This Master Thesis is an analysis of Best Practice in Danish companies in relation to integrated management systems. Integrated management systems in this regard particularly refer to the integration of quality, environment and OH&S management systems. Existing theories and integration models are analyzed and an analytical framework is developed that is used to establish the extent to which Danish companies integrate their different management systems. Existing experiences in relation to IMS, both in a Danish and international context, are also analyzed. IMS theories and models and existing experiences are used to guide a qualitative survey and quantitative case study conducted among Danish companies. It is found that Danish companies to a large extent integrated their quality, environment and OH&S management systems, and that there are a number of benefits associated herewith.