Tests for four letter-sound generalizations--"c" pronounced as [k] or [s] and "a" pronounced as [ae] or [e]--were given to 73 first, second, and third grade children at six-week intervals during a single school year. Each test included five synthetic words (e.g., cipe, acim, bice, cib, ocet) for each generalization. Children responded individually to the test items by attempting to pronounce each one aloud. The long and short pronunciations of "a" ([e] and [ae]) and the [k] pronunciation of "c" were learned to a high degree of accuracy. They showed no significant differences across grade levels, but did differ significantly across ability groups. For "c" pronounced as [s], however, learning was extremely low at all grade levels and reached only 45% correct by the end of grade 3. Initial "c" as [s] was learned more slowly than medial "c" as [s], indicating an interaction between letter pattern and word position. The failure to acquire the "c" pronounced as [s] pattern, especially in word-initial position, appears to result primarily from the failure of most beginning reading texts to include a sufficient sampling of words which begin with "c" before "e,""i," or "y." (Author/HS)