Although research on bilingualism in the schools shows the importance of measuring both English and Spanish language skills regularly, the testing of Spanish falls behind in both quality and frequency. Concerted multidisciplinary cooperation among bilingual educators, linguists, and psychometricians is now needed to produce a variety of valid instruments that simultaneously address the pedagogical and classificatory needs of bilingual programs as well as evaluators' and researchers' needs for versatile and accurate measures of educationally consequential skills. Tests currently used sometimes try not to identify limited-English students to save budgets, rest on questionable assumptions, purport to measure the impossible, do not guide users in the results, or present linguistically unrealistic demands. Academic achievement tests are often not well suited to Spanish speakers. The need is for tests that avoid the pitfalls of current measures, have high content validity and practical administrability, have scaling and categorizing systems well tested in groups with a meaningful range of language competencies at different grade or developmental levels, and measure all receptive and productive language modes. Additional techniques should be developed for testing bilingual teachers' professional and interpersonal language proficiency. (MSE)