Guideline VDI 3397 is concerned solely with metalworking fluids (MWFs) used in cutting or forming metals. In Part 1 the metalworking fluid is examined with regard to the tasks it must perform, its properties and its relevance to work safety and to the environment. Part 2 of the guideline deals with care of the metalworking fluid - in other words, instructions are provided on how from the economic and ecological points of view the service life of various types of MWF can be optimally extended while taking the relevant legislation into account. Finally Part 3 of the guideline provides information on reliable disposal methods. In general it is true to say that even at an early stage in selecting the MWF it is not only the price of the MWF itself but also the costs of care and in particular of disposal which should be the decisive economic and technical criteria for the user of the metalworking fluid.