This paper addresses the lack of language dominance assessment instruments and curriculum materials for Greek-speaking children in the U.S. These children need appropriate language screening tests, based on research and data derived from their native language group, for diagnostic and placement purposes. The development of an instrument for language assessment of Greek bilingual children is presented and traced. The subjects for the development of the instrument were 403 male and female first through fourth grade students enrolled in bilingual programs in the U.S. The final instrument consists of 80 items, 40 for the Greek and 40 for the English text, 30 of which are designed to elicit a response to a verbal stimulus using multiple choice pictorial alternatives. Each multiple choice item consists of a word stimulus to be matched to one of a series of five related pictures that follows. The remaining items are verbal stimuli in sentence form, designed to elicit a grammatically and syntactically correct answer to a question. Examination of the instrument in relation to field-test data, internal consistency reliability, test-retest reliability, reliability by school and sex, and validity demonstrated that the instrument possesses high reliability and usable validity values. (Author/JK)