Abstract: Serum samples were collected from commercial layer and broiler flocks 3 to 63 weeks old at four areas from Sudan. All flocks were not previously vaccinated against infectious bronchitis (IB) virus. Sera were tested using haemagglutination inhibition (HI) test for IB virus antibodies. 689(71%) out of the 957 samples examined had an HI titer ranging from 6 to 11 (log ). High incidence (90%) of IB virus infection was detected among layer flocks at Khartoum State and 46.8% of the samples had an HI titer > 10(log ). Low HI titer (<4 log ) was detected among samples collected from layer flocks at Sennar (Central Sudan). The results obtained indicated widespread and distribution of IB virus infection in Sudan.