We seek to further our understanding of English phonology and of the way in which phonological structure affects children's learning of printed English. Two specific aspects of phonology are examined -- the structure of the syllable and the division of two-syllable words into syllables. With regard to syllable structure, recent behavioral and linguistic evidence suggests that the syllable is not just a line string of individual sounds or phonomes. Rather, the phonemes may have a hierarchial internal organization, being grouped into an onset (initial consonant or cluster) and a rime (vowel plus any following consonants). With regard to syllabication, different linguistic theories offer different rules for the division of words into syllables. Some suggest that a phoneme may belong simultaneously to two syllables, or be ambisyllabic. The proposed research uses several techniques to gather information about syllables and their structure, including Pig Latin-type word games and error in short-term and long-term memory tasks. Based on the finding about phonological structure, the proposed research studies children's awareness of phonological units. It is hypothesized that children become aware that syllables can be divided into onset and rime units before they are able to analyze onsets and rimes onto their component phonemes. To test this hypothesis, experiments on phonological awareness of children aged 4-7 are carried out. It is further hypothesized that many of children's early spelling errors make sense when viewed in light of phonological theories about syllables. To test this hypothesis, computer-assisted analyses of a large collection of first graders' spellings are carried out.