1. The seven bacterial viruses of the T group active against E. coli, are rapidly inactivated at gas-liquid interfaces.
2. The kinetics of this inactivation whether brought about by shaking or by bubbling with nitrogen are those of a first order reaction.
3. This inactivation may be prevented by the addition of enough protein to maintain the gas-liquid interface in a saturated condition.
4. The analogy between this phenomenon and the surface denaturation of proteins is pointed out and discussed.