Infants begin to learn various features of their native language before they speak. Prosody is one of those features that infants learn at a very early developmental stage and plays an important role in language acquisition. This paper reviews previous developmental studies on prosody perception and production, and discusses future subjects. The role of prosody is first described in language discrimination, speech discrimination, and word segmentation from fluent speech. The paper follows by focusing on acquisition of stress accent in English and pitch accent in Japanese.