A study was designed to evaluate the efficacy of a recombinant feline omega interferon (rFeIFNw) in the treatment of canine parvovirus disease. In a multicentric, controlled, randomised and double blind clinical field trial, 177 dogs were included with a clinically diagnosed parvovirosis confirmed by ELISA and haemagglutination test on faeces. Eighty five dogs were given 2.5 million units (MU) interferon per kg body weight intravenously once a day for 3 days and 92 dogs received a placebo. Symptomatic treatment including rehydration, antibiotics, spasmolytic and antiemetic drugs was implemented for both groups. Dogs were clinically observed 6 times for 9 days and death date was recorded if appropriate. Efficacy was assessed through the survival probabilities which were calculated by the KAPLAN-MEIER method and compared by the LOGRANK test. 8 (9.4%) dogs died during the observation period in rFeIFNw group and 18 (19.6%) in the placebo group. Comparison of the survival curves showed a statistically significant difference between groups (p = 0.0300). Safety of the product based on clinical examination was excellent. After 3 IV injections of 2.5 MU/kg rFeIFNw , the survival probability was significantly higher in treated dogs than in placebo, with the mortality rate being 2.3 times lower in the treated group.