Olfactory memory is especially persistent. The current study explored whether this applies to a form of perceptual learning, in which experience of an odor mixture results in greater judged similarity between its elements. Experiment 1A contrasted 2 forms of interference procedure, "compound" (mixture AW, followed by presentation of new mixtures each containing 1 of its elements, AX and DW) and "elemental" (mixture CY, followed by presentation of its elements C and Y) against a nonexposed control. Learning was evident in both interference conditions to the same degree, relative to the control. Experiment 1B established that the interference conditions did not significantly differ from uninterfered paired controls. Experiment 2 compared the "compound" procedure with 2 exposed control conditions and assessed whether participants had acquired the interfering mixtures too (AX and DY). Learning was evident in the "compound" treated pair (AW) and also for the mixtures AX and DW that made up the interfering compounds. These results are problematic for configural explanations and a new formulation is suggested. (Contains 2 tables.)