Present study was carried out on 180 Crna Slavonska pigs, equally divided on barrows and gilts, distributed into two rearing systems: 80 animals were kept in indoor and 100 outdoor. Every three months, pigs from both experimental groups were sacrificed for growth analysis of muscle and fat in the series of subsequent dissection trials covering a total fattening period of 15 months for the pigs from indoor rearing system and 18 months for those kept outdoors. In first 4 trials covering the period from 3^rd to 12^th months of age, 8 pigs were sacrificed, while from thereafter to the end of investigation the number of pigs sacrificed for the dissection increased to 12. The results showed that rearing system had significant influence on the development of live weight, muscle tissue and fat of Crna Slavonska pigs. The differences in these traits between the Crna Slavonska pigs from two rearing systems were most pronounced at the end of fattening period, especially for the live weight and fat. Rearing system significantly affected also the gains of live weight, muscle tissue and fat in the way that indoor reared Crna Slavonska pigs had similar growth patterns of live weight and fat gain. In the last period of fattening the gain of muscle tissue began to stagnate while fat growth was increased. This trend was not observed for the muscle tissue gain of pigs kept outdoor. The results of present study pointed out that the production of lean and lean/fat ratio of Crna Slavonska pigs could be optimized. Further investigations of growth characteristics of Crna Slavonska pigs kept under different environmental conditions were recommended.