Year 2 findings are reported from a longitudinal, experimental-control study involving 31 Spanish-speaking preschoolers (aged 38-48 months) randomly assigned to two Head Start classrooms. In Year 1, classrooms differed only in the language of instruction, with teachers using only Spanish in one classroom and only English in the other. In Year 2, an experimental transitional bilingual education (TBE) model was implemented, with English being gradually introduced in the TBE classroom until a ratio of 30:70 English-to-Spanish was achieved and Spanish being gradually introduced in the predominantly English (PE) classroom until a ratio of 70:30 English-to-Spanish was achieved. Year 2 results were consistent with Year 1, with the TBE classroom exceeding the PE classroom on all Spanish measures of language and literacy development and no significant differences favoring the PE classroom. Results also indicated that Year 2 trajectories were conditional on first-year effects, suggesting that sustained growth in dual language learner's early literacy may depend on early intervention among 3-year-old preschoolers. (author abstract)