The objective of the present study was to determine the effectiveness of yeasts in broiler diets, on the basis of growing performance, nutrient digestibility and carcass dressing percentage. Dried, inactive molasses yeasts (Saccharomyces) were used in the experiment. This study was performed on 144 one-day-old Ross 208 codriarel chicks divided into 3 groups, 48 chicks each (six replications, eight birds each, within each group). The cockerels were kept in three-tier cages. They were reared in controlled environmental conditions until the age of 39 days. The diet given to group C (control) was not supplemented with dried yeasts. It contained animal protein (5%) in the form of meat meal. Dried yeasts in the amount of 3% (starter diet) and 5% (grower diet), and 5% and 7.8% were added to diets for groups E-1 and E-2, respectively. Yeast supplementation of the diets allowed to reduce soybean meal content by 2.5 to 4%, and to replace completely meat meal in the grower diet for group E-2. The results indicated that, diets for broiler chicks can be supplemented with molasses yeasts. Yeasts added In the amount of 7.8% to diets for Ross 208 cockerel chides reduced the digestibility of N-free extracts, but had no effect on body weight gains, feed consumption and survival rate or carcass dressing percentage. Adding yeasts to diets for broiler chicks increased feed cost per kg BW gain by 8 to 14%. The wed was carried out within the University of Warmia and Masuda prefect No 522.0104.221