Ferrets are subject to a number of important viral diseases. This chapter deals with the three important systemic viral diseases of ferrets; distemper, parvovirus (Aleutian disease) and rabies. Canine distemper virus (CDV) is an RNA virus of the genus Morbillivirus (family Paramyxoviridae), closely related to human measles virus. Aleutian disease virus (ADV) is a parvovirus that affects both mink and ferrets. It is so called because when discovered in the 1940s in the USA it affected the Aleutian genotype most severely. Rabies is an acute fatal encephalomyelitis caused by viruses of the genus Lyssavirus (family Rhabdoviridae). Ferrets are susceptible to rabies but in the USA fewer than 30 cases have been reported since 1958. The chapter details transmission, pathogenesis, clinical signs, treatment and prevention and control for Distemper, Aleutian disease and Rabies.