An outbreak of Salmonella typhimurium in an upland sheep flock was characterised by rapid spread and heavy mortalities in ewes and young lambs. Clinical signs included diarrhoea and abortion. Abomasitis was the most striking and consistent post mortem lesion. Vaccination was the only control method that was apparently successful. Infection also occurred in the cattle, farm personnel, and a dog. Following the outbreak, pasture contamination and excreting cattle provided a reservoir of infection so that contamination of water courses and sporadic cases occurred over a year later.