The Authors report the isolation in Italy of Feline Immunodeficiency Virus (FIV) from a cat inoculated with whole blood from a naturally FIV infected cat. The virus was isolated in feline circulating leucocytes cultured in RPMI medium and stimulated with concanavalin-A and recombinant human interleukin-2. The infected cultures showed a characteristic cytopathic effect (ballooning degeneration, giant cell formation, cell death) and a specific fuorescence using FIV-positive cat serum and monoclonal antibodies against FIV. Furthermore, the culture supernatants contained magnesium-dependent reverse transcriptase activity.