Several English and Spanish language tests currently used in bilingual education and some less known tests are reviewed, looking at both historic and psychometric factors. It is suggested that practitioners have commonly assumed that all language tests are basically valid, which contributed to the commercial success of some tests of questionable validity, ill-suited to the purpose of educational decision-making. Issues discussed include the various notions of and assumptions about language proficiency and language dominance reflected in them, reliability and validity, and considerations in test selection. Appended materials include a graphic representation of how language dominance and language proficiency interact at various levels, and a brief review of three tests: the IDEA Oral Language Proficiency Tests; Language Assessment Scales; and the Woodcock Tests. Contains 26 references. (MSE)