Information is presented from 4 different types of mouse tumor carcinoma NT'', slow carcinoma Rh, squamous carcinoma D, slow sarcoma S where animals have been restrained individually for irradiation in specially designed boxes to minimize the stress factors, either without anesthetic or while anesthetized with Sagatal. Anesthetics can modify the response of tumors to radiation, but in the present studies the effect is barely significant, except in the carcinoma Rh, and goes in opposite directions in 2 of the tumors. Where anesthetics can be avoided without causing excessive stress to the animals, this is clearly desirable. When using an anesthetic, the possibility of it inducing some alteration of response, which could be either protection or sensitization, cannot be excluded and the magnitude of this alteration would have to be determined for each system.
