Four outbreaks of bovine respiratory disease (BRD) associated with bovine coronavirus (BCoV) infection in Italian cattle herds were reported. In 3 outbreaks, BRD was observed only in 2-3-month-old feedlot calves, whereas in the remaining outbreak, lactating cows, heifers, and calves were simultaneously affected. By using reverse transcription polymerase chain reaction (RT-PCR), BCoV RNA was detected in all outbreaks without evidence of concurrent viral pathogens (i.e., bovine respiratory syncytial virus, bovine herpesvirus type 1, bovine viral diarrhea virus, bovine parainfluenza virus). Common bacteria of cattle were recovered only from 2 outbreaks of BRD: Staphylococcus spp. and Proteus mirabilis (outbreak 1) and Mannheimia haemolytica (outbreak 4). A recently established real-time RT-PCR assay showed that viral RNA loads in nasal secretions ranged between 3.10 x 10(2) and 7.50 x 10(7) RNA copies/microl of template. Bovine coronavirus was isolated from respiratory specimens from all outbreaks except outbreak 1, in which real-time RT-PCR found very low viral titers in nasal swabs.