Vegetables commonly consumed in Thailand were analyzed for their vitamin C, tannin and total phytate (inositol penta- (IP5) and hexasphosphate (IP6)) contents. Three conventional household cooking methods, namely blanching, boiling and stir-frying, were used to evaluate the effects of cooking. IP5 and IP6 content were determined using ion-pair reverse-phase chromatography. Vitamin C and tannin content were analyzed spectrophotometrically.