Noting that the last 40 years have witnessed an enormous increase in the number of psychological tests designed for the assessment of competencies in very young children, this review summarizes the quantitative and qualitative characteristics of psychological tests and other assessment instruments used to evaluate the cognitive functioning of infants, toddlers, and preschool children. The review is presented in three parts. Part 1 summarizes general principles of early childhood assessment. Part 2 describes the major domains in which the various assessment tools can be compared, evaluated, and selected. Part 3 presents brief descriptions and evaluations of selected instruments. Appended is a list of 313 additional references regarding specific tests or the assessment process. (Contains 103 references.) (KB)