Metabolic changes were studied in embryonic axes and cotyledons isolated from after-ripening seeds of Prunus cerasus. During the seventh week of after-ripening, a striking increase in the respiration rate at 25 degrees of embryonic axes occurred along with a sharp change from the dormant to non-dormant state of the seed. On the basis of C-6/C-1 ratio determinations this change may be related to an increased activity of the pentose phosphate cycle.