This paper describes the development and implementation of an intensive summer course in English as a Second Language (ESL) designed for children aged 4-5. Planning included development of a curriculum and instructional materials based on theory and practice in the teaching of young children, English language learning and instruction, and curriculum development. The teacher had native-like English skills and limited conversational ability in the children's first language (Japanese). A Japanese-speaking aide was available for emergency interpretation. No effort was made to foster the children's first language or culture in the course. A theme-based curriculum with topics of interest to young children was devised. It was implemented in a six-week half-day course at an Okinawa (Japan) private school. Curriculum and classroom components common in preschool education were also used here, including learning centers, pre-literacy exposure to English, and work tasks to reinforce past content. Teacher journals, student pre- and post-course evaluations, and students' expressive language samples were used to analyze course effectiveness. Results indicate that the short-term immersion course is a viable and effective method of teaching English to young children. Recommendations for classroom practice and for instructional materials development are also made. (MSE)