Abstract: The application of gibberellin to Mentha arvensis L. (Chinese peppermint) induced the prolongation of the internodes. The plants were twice as tall as those of the control plants and the leaves were slightly chlorotic. The following effects were also noted in the treated plants: (1) 30.6—126.3% increase in the dry weight of stems, (2) 3—41.1% reduction in the dry weight of leaves and tops, (3) 0.02—1.02% v/w reduction in the volatile oil yield (3.31% v/w in the controls) and a lower content of menthol.