Feline infectious peritonitis (FIP) is a fatal disease in cats. The disease results from widespread viral replication in affected animals and an inadequate and harmful immune response to the virus. Currently, there is no effective treatment for this disease. Though therapies aimed at improving the immune response to this virus have shown some benefit, there is a need for an additional therapy to specifically inhibit virus growth in order to effect a successful treatment. Recently, RNA interference has been shown to be useful for treating virus infections. This antiviral mechanism results from the introduction of double stranded RNA into cells that specifically target the virus and thus lead to its destruction. This strategy has been used successfully experimentally to treat Severe Acute Respiratory Disease (SARS), a virus that produces a disease similar to FIP in humans. In addition, this strategy has been shown to be effective against a feline virus, feline herpes virus. It is hoped that suppression of viral infection, combined with a treatment to improve the immune response against FIP, will provide a successful treatment, if not a cure, for FIP.