Transmissible gastroenteritis (TGE) is an acute, rapidly spreading, viral disease of swine of all ages, characterised by diarrhoea and vomiting. It is caused by TGE virus (TGEV), a member of the Coronaviridae. High mortality in piglets under 2 weeks of age is common with mortality decreasing with age. There also is an endemic form of the disease, seen in herds with partial immunity or concurrent porcine respiratory coronavirus (PRCV) infection, with less severe signs and much lower mortality. TGE occurs naturally only in swine. Among previously unexposed swine, all age groups are susceptible. In acute outbreaks, the incubation period is very short, 18 hours to 3 days. In baby pigs the disease spreads rapidly to affect all susceptible pigs. Signs include profuse diarrhoea, frequent vomiting, rapid dehydration, shivering and marked thirst. The pigs weaken rapidly and usually die within 1 to 2 days. Pigs suckling immune dams may remain well as long as they receive adequate antibody in the dam’s colostrum and milk. Pigs infected after 4 weeks of age often survive. The chronic or endemic form of TGE often is seen in pigs from herds where some dams are immune and others have a limited immunity. Onset of clinical signs varies, but is usually later in lactation or early in the postweaning period (2 to 5 weeks of age). Signs can be rather mild and usually include diarrhoea, dehydration, unthriftiness and runting. In feeder and fattening pigs, signs usually are mild except for diarrhoea, which is profuse and watery for a few days. Vomiting occurs occasionally. Morbidity is high but mortality is low or absent. Moderate severity is observed in naïve sows and gilts, especially in those that have farrowed recently and are heavily exposed to virus from piglets with TGE. The dams show anorexia, vomiting, diarrhoea, depression and may cease to lactate. Recovery usually occurs within 5–10 days. Attenuated and killed virus vaccines are available.