Sustained farming may be assessed with the use of ecological, social and economic measure. Ecological assessment of the sustainability degree of farms was carried out with the use of sustainability of organic matter balance. Moreover, production organization in the researched farms was described. The analysis covered 15 farms of Śląskie voivodeship, which specialize in milk production. The selected facilities have the features of sustained farms concerning inter alia, the structure of the land use and sowing as well as livestock. The research was carried out in the form of a guided survey with farm owners. Data concerned 2012. In order to carry out comparative analysis, the facilities were divided into groups, assuming area of agricultural land as a division criterion. Therefore, 3 groups we distinguished: I of area up to 20.00 ha, II - from 20.01 to 50.00 ha and III of the acreage exceeding 50.00 ha of agricultural land. In all groups, excess of NPK components was reported and the index of sustainability of organic matter within the limits, occurred only in the smallest farms.