Corosolic acid content and distribution in Lagerstroemia speciosa Pars. were investigated, indicating that the red leaves contained more corosolic acid than the green leaves and other plant parts such as petals, roots and seeds. The leaf redness was derived from cyanidin 3-O-glucoside which was first identified in this species. The contents of corosolic acid and cyanidin 3-O-glucoside were found to be well correlated, supporting the traditional perception of local people of the Philippines that red leaf banaba tea exerts more pronounced medicinal effects.