The purposes and methods of testing in bilingual and English-as-a-Second-Language (ESL) education are discussed. Different instruments, including specific published tests, are listed and described briefly. They include language proficiency assessments, achievement tests, and assessments in special education. Introductory sections address topics surrounding the testing itself, including the need to understand the purposes of the testing and of a specific test, the information needed about a student, specific uses of that information, when it is appropriate to test the student, and defining second language proficiency. (Contains 20 references.) (MSE)