Aleutian disease virus, the causative agent of a persistent infection in mink, was isolated in a continuous line of feline renal cells when the cultures were maintained at reduced temperature (31.8°). After serial in vitro passage of the virus at this temperature it had an optimum replication temperature of 37°. An immunofluorescence focus assay was found to be suitable for virus quantitation. The cultured virus reproduced Aleutian disease in mink, and the virus could be reisolated from the mink 10–180 days after inoculation. The properties of the virus suggest that it is a member of the parvovirus group.