The primary purpose of this study was to calculate the fattening costs of different cattle breeds reared under controlled conditions and to determine the optimal fattening period that will maximize the net profit. The data were from 21 bullocks consisting of 7 Holstein, 7 Piedmont x Holstein, and 7 Limousin x Holstein cross-breed cattle reared and fattened in the closed tie-stall experiment barns of the Aegean Agricultural Research Institute, Turkey. The data used for the analysis were from the year 1999, but were updated for 2007. The fattening period lasted 280 days, after a rearing period of 195 days. The average live weight, costs of 1 kg live weight, yield ratio, and net profit per animal at the end of fattening period were 510.86 kg, YTL 3.65, 57.36%, and YTL 462.33, respectively. The Limousin breed yielded the highest net profit. The optimal fattening period was 5 months. Net profit increased by 21.67%, while the costs of 1 kg live weight decreased by 13.97% at optimal fattening relative to the fattening period in the application. Live weight, yield ratio, meat price, gross production value, production costs, and net profit per animal differed significantly among the Holstein, Piedmont, and Limousin breeds. The results indicated clearly that the optimal fattening period (5 months) yielded much more net profit in comparison with the fattening period in the application. It appears possible to arrange different plans for different cattle breeds.