ABSTRACT The introduction of commercial infectious bronchitis vaccines to be administered in the drinking water made it desirable to determine the survival time of this virus in water. Initially, a pathogenic strain of IB which is routinely used at this laboratory to challenge birds for immunity against IB was used to determine its survival time in triple-distilled water buffered at different pH and kept at 25°C. for various periods of time. The inoculum consisted of chorioallantoic fluid of chicken-embryonating eggs which had been infected with IB virus. A previous titration of this strain (Massachusetts strain L43g7) in two-month-old susceptible chickens indicated an infective dose 50 of l0−6.17. Three 250 ml. Erlenmeyer flasks were used in this experiment, and each flask contained 50 ml. of the IB virus diluted 1:50 in tripledistilled water. The distilled water was buffered with Sorensen solutions a t pH 6.39 in the first flask, at pH . . .