A callus was induced from the petiole of Panax ginseng C. A. Meyer by treatment with 2,4-D. The callus has been maintained on the synthetic media containing 2,4-D as growth factor. Habituated ginseng callus which required no auxin for its growth was induced from a 2,4-D callus by successive treatments with a low concentration of 2,4-D. The fact that the process of habituation is reversible suggests that its mechanism is based upon adaptation rather than rare mutation followed by selection. It was also shown that the capacity of saponin production is significantly lower in habituated callus than in normal callus. Habituated callus which was maintained on 2,4-D media gradually recovered its capacity for saponin production and the degree of this capacity seemed to parallel the degree of its requirement for auxin.