Over half the world's population speaks a tone language, yet infant speech perception research has typically focused on consonants and vowels. Very young infants can discriminate a wide range of native and nonnative consonants and vowels, and then in a process of "perceptual reorganization" over the 1st year, discrimination of most nonnative speech sounds deteriorates. We investigated perceptual reorganization for tones by testing 6- and 9-month-old infants from tone (Chinese) and nontone (English) language environments for speech (lexical tone) and nonspeech (violin sound) tone discrimination in both cross-sectional and longitudinal studies. Overall, Chinese infants performed equally well at 6 and 9 months for both speech and nonspeech tone discrimination. Conversely, English infants' discrimination of lexical tone declined between 6 and 9 months of age, whereas their nonspeech tone discrimination remained constant. These results indicate that the reorganization of tone perception is a function of the native language environment, and that this reorganization is linguistically based. (Contains 4 figures and 4 footnotes.)