The aim of this paper was to assess the level of air contamination by bacteria and fungi in broiler houses. The numbers of bacteria (mesophile, staphylococci, streptococci and gram-negative) and fungi were determined in broiler houses with chicken of different ages (1-6 weeks old). The results showed high levels from bacterial contamination in broiler houses air. The mean number of bacteria ranged between 2×10⁶ – 9.81×10⁶ cfu/m³ for the total number of mesophilic bacteria, between 1.20×10⁶ – 5.59×10⁶ cfu/m³ for staphylococci, between                    0.13×10⁶ – 0.97×10⁶ cfu/m³ for streptococci, and between 0.086×10⁶ – 0.423×10⁶ cfu/m³ for gram-negatives. The mean fungi levels were middle and ranged between 88 ×10³ to 145×10³ cfu/m³. The proportions of bacterial groups within the total mesophilic bacteria number were: 46.6 - 60 % staphylococci, 2.3 - 28.5 % streptococci and 1 - 7.4 % gram-negative. In general, the number of bactria increased with poultry age and it was high in the mid-fattening period but the number of fungi did not increase with the chicken's age. The results indicate the necessity for increased ventilation and for air disinfection during the chicken's fattening period.