Using the technique of "panels" farms were drawn as representatives from three regions of Brazil: the first was a medium size farm representing the grain production area of Northern Rio Grande do Sul State; the second, a large farm from the grain and livestock production area of Mato Grosso State; the third, a very large farm from the Amazonian livestock production area of Para State. The long-term cost of production was estimated and the yearly average net income was evaluated for each typical farm. An "energy" evaluation table, prepared according to procedures described by Odum (1996), was used to estimate each farm process of incorporating energy into its production as a way to evaluate the sustainability of the farms systems. A four quadrant reference system, based on the average measurements for each vector - environmental accounting and net farm income - allowed the plotting of the three farms on the designed quadrants. The null hypothesis indicates that sustainable farms must be plotted on the southwest and on the northeast quadrants. The presence of farms on either of the two non-expected quadrants, the northwest and the southeast, poses long term problems of sustainability and indicates that new development policies are required.