A total of 426 serum samples were examined from 9 broiler and 7 broiler breeder flocks showing clinical signs of swollen head syndrome (SHS) Turkey rhinotracheitis virus antibodies in 8 broiler flocks were between 31.8 and 75.9% and in broiler breeder flocks between 5.4 and 48.6%, with a commercial ELISA. Typical clinical symptoms were observed for SHS in broilers and broiler breeders. During the study, turkey flocks showing clinical signs were not detected. The antibodies to TRTV were between 5.5 and 80.0% in 7 out of 10 broiler flocks, and between 20.0 and 57.1% in 3 out of 4 fattening turkey flocks, 10.5 and 11.1% in 2 out of 6 breeder turkey flocks. In the bacteriological investigation, a total of 38 E. coli isolates were obtained from 9 broiler and 2 broiler breeder flocks. In addition, 6 S. aureus, E. Staphylococcus sap. and 2 Streptococcus ssp. were isolated from these flocks. The antibiotic sensitivitiy test revealed that all 38 E. coli isolates were sensitive to apramycin. Histopathological lesions were present especially in the subcutaneous tissue of the head and upper respiratory tissue.