Background:Banaba (Lagerstroemia speciosa, Lythraceae, Pride of India) is a medicinal plant that grows in the Philippines, Japan, India, Southeast Asia, etc. Traditionally, the leaves are used to treat diabetes and hyperglycemia. This effect is attributed to its chemical constituents belonging to the groups of terpenoids, tannins, and flavanoids. The objectives of this paper are to present a new method of identification and quantification of corosolic acid, a terpenoid, using HPTLC. Material and methods:The hydroalcoholic extract of leaves was chromatographed on aluminum plates coated with silica gel 60F254, with Toluene: Acetone: Formic acid (5:2:1 v/v) as the mobile phase. Densitometric quantification of corosolic acid was performed after derivatization with 10 % methanolic sulphuric acid in fluorescence mode at 366 nm. Results:Amounts of corosolic acid (at 366 nm, Rf value = 7.2) in the sample was calculated using regression equations (R 2 = 0.9959 (366 nm) of calibration plots, which showed there was a good polynomial relationship between peak area and amount of corosolic acid in the range 250-3000 ng/band. The limits of detection (LOD) and limits of quantitation (LOQ) were 70 and 245.6 ng/band, respectively. The method was validated for precision and accuracy. Recovery was determined by spiking the extract with corosolic acid standard and found to be in the range 94.4-96.5%. Conclusion:The corosolic acid content found in the leaves was 1.5% w/w at 366 nm.