In testing the hypothesis that ether anesthesia immediately following a single conditioning trial impairs the retention for the response thus conditioned, six groups of 20 mice were tested. Three groups were conditioned in a single trial and three groups served as controls. An experimental group and a matched control group were either: (1) anesthetized with diethyl ether immediately following the response (2) anesthetized one hour following the response or were (3) not anesthetized. The results showed that immediate ether anesthesia was effective in impairing the retention of the avoidance response. One hour postconditioning etherization had no apparent effect on retention, and ether anesthesia did not alter the responses of control subjects.