The cotton plant among the cultivated crops has the most allelochemicals in kind and quantity, yet it is highly vulnerable to insects and pathogens. This paradox has perplexed the investigators on the molecular bases of cotton HPR. A model on cotton and insect pest interaction has evolved from our integrated studies in the past years, especially of Heliothis zea/cotton interaction. We had carried out extensive chemical Teterminations of the allelochemicals (cycloprenoids, terpene aldehydes and its analogs and flavonoids) with respect to their distributions in the cotton floral organs and the ontogeny of these organs. We had studied their physiological effects on the insects and the insect feeding behavior. We will summarize our results and present our conclusion.