This Masters thesis is a qualitative study of three examples of Danish companies in relation to the needs of the companies and the levels of integrated management systems. Integrated management systems here refer to the integration of quality, environment and OH&S management systems. Focus is placed on the levels of integration. Existing theories, integration models and experiences are analyzed and an analytical framework is developed which is used to determine the needs of companies, the integration model and level that best suits the different levels of integration. Existing experiences in relation to IMS, such as the incentives, disadvantages and benefits are also analyzed and related to the levels of IMS. And it is seen that the incentives and benefits are related to the levels of integration, meanwhile there are almost no difficulties faced. It is also found that all three companies integrate their management systems to at least the coordinated level. The factors that determine the levels of integration are the size, functioning, competition, institutional setting, kind of system and all these depend on the needs of the companies as well as the needs could be determined by all these factors.