This article reports the outcomes of a multiyear study comparing the English and Spanish language and reading performance of Spanish-dominant children randomly assigned, beginning in kindergarten, to transitional bilingual education (TBE) or structured English immersion (SEI) for periods of up to 5 years. On the Peabody Picture Vocabulary Test and its Spanish equivalent (Test de Vocabulario en Imagenes Peabody) and on the English and Spanish versions of three Woodcock Reading Scales, first graders in TBE performed significantly better in Spanish and worse in English than did their SEI counterparts. Differences diminished in second and third grades, and by fourth grade, when all students in TBE had transitioned to English-only instruction, there were no significant differences on English reading measures. These findings suggest that Spanish-dominant students learn to read in English equally well in TBE and SEI and that policy should therefore focus on the quality of instruction rather than on the language of instruction for English-language learners. (Contains 1 note and 8 tables.)