This paper presents a "Language Background Questionnaire" designed for use in gathering information on the home linguistic environment of bilingual children. The questionnaire probes a series of demographic and environmental variables which define a bilingual child's sociolinguistic milieu. Instructions are given for calculating the overall respective language use in the home as well as language specifically directed to and from the child in terms of the mean language input and the mean language output. Questionnaire scoring is arranged for easy adaptation to computer programs. A reliability check found the method of self-report used in the questionnaire to be 75% reliable. The questionnaire is appropriate for use by both researchers and educators in studying and evaluating language development in bilingual children. (Author)