Introduction Greening and eco-friendly activities within the agricultural primary pro-duction are currently playing an important role not only in the Slovak Re-public. Within these activities and considering the environmental impact of agricultural technology, there is a possibility of applying ecological lub-ricants in transmission-hydraulic systems. Our scientific monograph pre-sents the results of long-term service life tests of selected ecological lubri-cants. Before applying ecological lubricants in working machines, these lubricants have to be subjected to laboratory tests since the manufacturers of agricultural technology only minimally recommend the application or use of these lubricants. In case of application of plant-based ecological lubricants, it is necessary to monitor their effect on operating parameters of transmission-hydraulic systems, their degradation process in laboratory or in-service tests and the way of their contamination by external or inter-nal (abrasion) adulterants and by chemical elements. It is also necessary to monitor their effect on the most important machine components. Determination of possibilities to apply plant-based ecological lubricants enables to determine their technical worthiness for use. The use of these lubricants is necessary in ecologically sensitive areas (drinking water sources, protected areas) or in organic farming on agricultural lands. The above mentioned prerequisites can be fulfilled by legislative intervention of the government (European Union), or by tax/subsidy measures.