To investigate the actual and possible roles of parents in the development of preschoolers' bilingual ability, this study examined the home environments and bilingual ability of Singapore preschoolers. A total of 378 children, aged 5 and 6 years, were divided into 2 groups and individually interviewed. Children in one group began the interview in English; the other group began the interview in Chinese. During the interview, children were tested in English and Chinese in the areas of vocabulary, listening comprehension, story comprehension, translation, and verbal fluency. Children also completed a Home Language Environment Questionnaire. The children's parents also completed questionnaires. Analysis showed that children who perceived their home environment to be predominantly bilingual produced optimal performances in both English and Chinese language tests. Most parents were actively involved in helping their children develop language ability either directly or indirectly. Results also revealed that while children performed well in all language tests, there were some common areas of weakness in both languages, as well as important differences in certain corresponding aspects of English and Chinese, which could affect interlanguage transfer. (MM)