The polymethoxyflavones (PMFs) found in citrus peels are a complex family of natural compounds reported to exert a variety of biological effects in vitro and in vivo including anti-tumor, anti-inflammatory, anti-hyperglycemia and anti-hyperlipidemia etc.There are a few marketed products whose major ingredients are from citrus peel extracts,including both oral and topical preparations.Even though the forms, applied dosages and the therapeutic claims of these products vary, efficacy is supported by both in vitro testing and preclinical as well as clinical trials.We found that a product from natural citrus peels is very efficacious in treating human cancers, including lung cancer, liver cancer, prostate cancer, leukemia, stomach cancer etc.This presentation will describe our methodology and findings from the application of a citrus peel product, currently marketed as cosmetic use, on human cancers as well as the correlation between its content ofpolymethoxyflavones which has been accurately measured in our research laboratory and the effective dosage to warrant efficacious effects in treating human cancer.