Feline immunodeficiency virus (FIV) is a retrovirus causing significant disease in cats. The virus has been shown to be similar biologically to the human immunodeficiency virus (HIV), the cause of acquired immunodeficiency syndrome (AIDS) in humans. Much interest has been expressed in the use of FIV as an animal model for HIV vaccination studies. Both FIV and HIV belong to the lentivirus group of retroviruses. While there are several effective vaccines against feline leukaemia virus (FeLV), a mammalian type C retrovirus, at present there are no effective vaccines against lentiviruses. This review illustrates the obstacles to the production of vaccines against FIV or HIV. FIV vaccine studies conducted in several laboratories are reviewed, the results are compared and factors important for inducing protection from FIV infection are discussed.