Infectious bronchitis (IB) continues to be a major cause of economic losses in the Ontario poultry industry. Infectious bronchitis virus (IBV) is one of the primary agents of respiratory diseases in chickens. In addition, IBV can cause poor egg quality and decreased egg production. The genetic and antigenic diversity of IBV strains is well documented and its consequences in poultry health are recognized. Proper vaccination programs are critical to control IB outbreaks. Therefore, it is essential to identify IBV strains circulating in an affected area in order to choose an effective vaccine for the region as an aid in the ongoing control of economic losses. To provide a background of the IBV situation in Ontario layers, sentinel birds were placed on 13 farms identified through a survey. The selected flocks had different histories of egg production losses and respiratory disease even though most farms were maintaining vaccination programs which included both live Massachusetts and Connecticut IBV vaccine strains. (Abstract shortened by UMI.)