Pavlovian conditioning of the natural killer (NK) cell response has been demonstrated by pairing camphor with polyinosinic: polycytidylic acid (poly I: C) in nine association trials. The NK cell response could be conditioned also by using combined saccharin and lithium chlorid (LiCl) as the conditioned stimulus. The camphor and saccharin‐LiCl paradigms were tested to determine if the conditioned NK cell activity was the result of conditioning of the interferon response. Interferon levels were measured at 6 hr and NK cell activity at 24 hr after application of the conditioned stimulus. The interferon levels measured in separate experiments were not uniformly elevated in conditioned animals compared with controls. Copyright © 1987 Alan R Liss, Inc.