This paper presents an assessment of organization change and economic effects in the process of conversion of the farm from conventional into organic farming system. The research was conducted in 2004-2007 at the Experimental Station Grabów of IUNG-PIB Puławy. The organizational and economic assessment was carried out by comparing a number of criteria and indicators commonly used in agricultural economics, such as plants yielding, efficiency of crop rotation, intensity of agricultural production, economic efficiency and economic size of farm. The changes of management in ES Grabów from conventional into organic farming cause in result a significant changes of production and economical ones. During the transition period it has been stated in the farm a reduction of cereals yielding and the overall crop rotation. During this conversion an income from farm increased on average of 42 %. The system of subsidies and the subsidy for organic farming was of great importance in achieving of this result. The value of direct payments for organic production composed approximately 20 % of the final gross production of farm and about 57 % of farm profit.