The purpose of this study was to develop, implement, and evaluate the efficacy of two intervention program packages adapted from evidence-based approaches, and designed to promote successful transitions to kindergarten for behaviorally at-risk preschoolers from Head Start organizations in Miami-Dade County, Florida. Fifty children identified by their preschool teachers as being at high-risk for problematic transitions to kindergarten due to externalizing behavior problems were randomly assigned to one of two groups. Group 1 (High Intervention) received a package of programs in which children's behavioral, social-emotional, and academic functioning were targeted using evidence-based approaches including a four-week adapted Children's Summer Treatment Program before the start of the kindergarten year. The program included weekly parent transitional workshops before the start of kindergarten, weekly parent transitional workshops after the start of the kindergarten year, and monthly school consultations and parent transitional workshops throughout the children's kindergarten year. Group 2 (Low Intervention) received the same series of parent transitional workshops, but the children did not receive the adapted Children's Summer Treatment Program or school consultation sessions throughout the kindergarten year. The children's transition to kindergarten was evaluated and compared in the fall and spring of the kindergarten year via parent and teacher report, and objective measures of behavioral, social-emotional, and academic functioning. Results from this study indicate that children receiving high intervention services prior to kindergarten entry had more successful transitions to kindergarten. This was demonstrated by fewer problems in their behavioral and academic functioning when compared to children receiving low intervention services. (author abstract)