A new clinicopathological disorder associated with a paramyxovirus infection in pigs is described. Central nervous system manifestations and corneal opacity are the main features in piglets two to 21 days old. Older pigs seem to be more resistant and only corneal opacity is commonly observed. In pregnant sows the virus appears to be responsible for reproductive disturbances such as stillbirth, mummification and a return to oestrus. The changes are mainly microscopic and characterised by a non-suppurative encephalomyelitis, interstitial pneumonia and anterior uveitis with corneal oedema. Experimental infection of one-day-old piglets with the virus reproduced clinical signs similar to those described in naturally infected piglets. The virus was recovered from the tonsils, lung and brain of the experimentally infected piglets between the fourth and 20th day after infection.