One of the most controversial doctrines to emerge in insurance law over the last forty years in USA is the doctrine of reasonable expectations. The doctrine of reasonable expectations is a principle that relies on the ‘reasonable expectations of the insured’ as a guide for insurance contract interpretation. Under the doctrine of ‘reasonable expectations’, courts often grant coverage to an insured even when the express language of the policy does not provide coverage. In its strongest form, the doctrine of reasonable expectations goes beyond contra proferentem, a traditional rule of interpretation. Contra proferentem grants coverage to an insured by construing ambiguous policy language against the insurance company. In contrast, the doctrine of reasonable expectations grants coverage when the insured has an objectively reasonable expectation of coverage even in the absence of ambiguous insurance policy language. This paper analyzes whether court in USA has adopted the doctrine of reasonable expectations. To provide the necessary historical background, this paper explores how other jurisdictions have approached the doctrine. Part II explains the contexts of the general doctrines for the contracts construction in American courts generally, while Part III describes the so-called "Keeton's formula" and researches the established theory about the applicable materiality of the doctrine, and presents the new approach about the applicable materiality by my opinion. Part IV analyzes the relations between the doctrine of reasonable expectations and the disclosure duty of insurer. Part V concludes that the Korean Court could accept the doctrine of reasonable expectations to a rule of insurance policy construction.