This chapter, prepared for a volume on Language Learning to be published by the National Council of Teachers of English, is a review of the development of language competence and performance skills beyond the years of primary language acquisition, i.e., from about the first grade on. First, development of specific skills relating to phonology, syntax, and vocabulary is reviewed, and then attention shifts to the development of "integrated skills": listening, speaking, reading, and writing. Emphasis is put on identifying dimensions of individual differences in rates of growth and development. Although a substantial degree of basic competence in the rules of the native language is attained by the normal child at school entry age, development is by no means complete at that time. In many aspects of language skill, development continues throughout the years of schooling and to a lesser extent throughout adult life. In adult populations, there are enormous individual differences in nearly all aspects of language skill. Gaps in our knowledge of factors in development are pointed out.