AbstractThe influence of LiCl preexposure on odor‐aversion conditioning produced by an odor‐LiCl pairing was studied in rats 7–31 days old. LiCl preexposure interfered with the acquisition of the odor aversion in both young and old pups. The time course of this effect depended, however, on the age of the pups. It lasted much longer (over 24 hr) if pups 8–17 days old were preexposed to LiCl than if the pups were preexposed when 30 days old (less 12 hr). Alternative interpretations of these data were discussed, and it was suggested that the age‐dependent differences in the time course of the LiCl preexposed effect may be determined in part by age‐related differences in the rat's excretory processes that clear lithium from the circula