The efficacy of iodine and glutraldehyde containing compounds against infectious bursal disease virus (IBDV) was assayed by comparing the virus titer before and after exposure to each disinfectant. The test was conducted at room temperature in presence or absence of organic matter “40% foetal bovine serum". The two tested disinfectants were effective against IBDV under all test conditions and at the dilutions used 1:50, 1:100 and 1:200. In this paper a new method for calculation of viral regression after disinfection, was devised as it gives a more reasonable calculation.