Controversy has long been beneficial to the scientific community, for out of controversy comes increased research effort and out of research come answers. More frequently, however, out of research come questions and out of controversy comes only confusion. Such is the current state of knowledge concerning coronaviral disease in cats and, specifically, feline infectious peritonitis (FIP). While much information abotu this disease, its pathogenesis and clinical course has been produced, significant questions still remain. There is a major division in thought among scientists concerning the cause and nature of FIP infection and at the heart of this controversy lies FIPV's relationship to one of two recently recognize enteric coronaviruses of cats.