As part of an initiative aimed at reducing the number of cattle deaths in Northern Ireland, a survey of bovine mortality on a stratified random sample of farms and veterinary practices was carried out during 1992. In the farm survey, over 3500 deaths were reported from 1069 farms, with a further 237 farms reporting no deaths during the year. The estimated numbers of deaths of suckler cows and dairy cows were 5997 and 4246, respectively, giving an estimated annual mortality rate of 2.36 per cent for suckler cows and 1.55 per cent for dairy cows. One third of the suckler cows and 19 per cent of the dairy cows were found dead with no previous signs of illness. In the cows in which clinical signs were observed and which received veterinary attention, hypomagnesaemia (20.3 per cent) was the main cause of death in suckler cows and coliform mastitis (12.3 per cent) was the single most important cause of death in dairy cows. Conditions associated with calving accounted for approximately 30 per cent of the deaths in both types of cow.