Abstract The effects of phenobarbital on taste aversion induced by X-radiation were examined. Rats were adapted to a 23 hr 50 min water deprivation schedule. On the Treatment Day animals were given a novel 0.125% Na saccharin solution during the 10 min drinking session and were then exposed to 100 rads of X-radiation. The saccharin solution was presented again on six subsequent Test Days. Phenobarbital in doses of 20, 40, 60 and 80 mg/kg was administered 15 min prior to drinking on the first Test Day. Results demonstrate that phenobarbital in all doses tested has a significant attenuating effect on radiation induced taste aversion.