A virus morphologically resembling members of the family Paramyxoviridae has been isolated from the brain of a piglet with a central nervous disorder accompanied by pneumonia and corneal opacity. The virus, designated LPM, grows in a large variety of cultured cell types and elicits a cytopathic effect including formation of syncytia and cytoplasmic inclusion bodies. The virus has hemagglutinating, neuraminidase and hemolytic activities. Studies on experimental transmission showed that young pigs are susceptible to infection which induced a disease similar to that in natural cases. The virus killed mice and chicken embryos. The structural proteins of LPM virus, as resolved by polyacrylamide gel electrophoresis are similar to those described for other paramyxoviruses. Serologically the virus proved to be distinct from the paramyxoviruses tested so far.