Since 1981 a highly contagious viral disease causing high morbidity and low mortality in racing pigeons has spread over Europe. The virus belongs to the avian paramyxovirus sero group I. Clinical signs include watery droppings, polydypsia and neurologic signs in a high proportion of infected animals. Definitive diagnosis can be made by virus isolation in cell cultures or chicken embryos, and virus identification by haemagglutination and haemagglutination inhibition (HI) tests. The HI test, using sera from suspected animals, is a useful clinical tool to confirm the diagnosis. The most important differential diagnosis is salmonellosis. Good immunity against this disease can be acquired by subcutaneous vaccination with an inactivated oil adjuvant poultry NDV-vaccine. For the benefit of pigeon racing a plea is made for compulsory vaccination in countries in which the disease is endemic.