The survival of infectious pancreatic necrosis (IPN) virus under conditions pertaining to its retention in the laboratory, and its inactivation by several physical and chemical means were examined.Approximately 99.9% of infectivity was lost when washed IPN virus (106.5–107.0 TCID50/ml), suspended in phosphate buffered saline (PBS) and Eagle’s Minimal Essential Medium diluted 1:10 with PBS, was held at 4 C for 1 yr. After 2 yr more than 102 TCID50/ml remained in both suspensions. The virus survived equally well for 1 yr in 20 and 50% glycerol.Thermal inactivation of IPN virus at 60 C proceeded in a two-component manner, each component following first-order kinetics. At neutral pH, the infectivity of 107 TCID50/ml was reduced by 99.9% in the first 30 min of exposure. After 5 h, 0.0001% still survived. Inactivation rate of the initial rapid component was increased by adjustment of pH to 3 and 10.The curve for the 1:4000 formalin inactivation of 106.5 TCID50/ml of IPN virus was multiphasic. When formalin-treated virus was titrated, cytopathic effect was delayed.Under a UV intensity of 2000 μW/cm2, the infectivity of 107 TCID50/ml of virus was lost exponentially during the first 6 min of exposure after which it abruptly leveled off. The curve was less steep and curvilinear under an intensity of 440 μW/cm2. The level of tailing was the same in both cases.IPN virus was predictably stable at pH 7 at 4 C. A surprising 0.001% of an original concentration of 107 TCID50/ml survived incubation at pH 9 and 2 for 5 wk. The reported survival of IPN virus in homeothermic animals was related to its ability to withstand prolonged exposure to low pH and to its relative heat stability.