This thesis investigates the interpretation of sentences with quantified phrases (QPs) in Japanese, with special consideration of the relation of interpretation to information structure. QPs in a sentence are known to interact with one another and produce a variety of interpretations, such as distributive readings and branching quantifier readings. In this study, we closely examine the conditions under which QPs may exhibit those distinct "scope" interpretations, and attempt to demonstrate that certain aspects of information structure play a significant role in their determination. In the course of the inquiry, we also observe that some scope interpretations are easier to obtain than others even among grammatically permitted interpretations, and propose an analysis based on the economy of derivation to explain such an interpretive asymmetry. We also identify a variety of factors that permit us to explain three empirical phenomena often reported in the literature: (1) why scope interpretations of QPs are so subtle and unstable; (2) why scrambling of the object QP over the subject QP often leads to scope ambiguity; and (3) why narrow focus on some QP has the effect of clarifying scope ambiguity. By shedding light on these otherwise obscure behaviors of QPs, we attempt to bring some order to empirical chaos and embark on the construction of an empirically sound foundation upon which present and future research can be based.