After providing a brief review of three other approaches to assessment of preschool children (DSM-IV diagnoses, "Zero to Three" diagnoses, and temperament scales), this paper focuses on the Achenbach System of Empirically Based Assessment (ASEBA). The empirically based assessment paradigm provides user-friendly, cost-effective, reliable, and valid procedures for assessing children's behavioral/emotional problems from the perspectives of multiple informants. The ASEBA preschool forms, the Child Behavior Checklist for ages 1.5-5 (CBCL/1.5-5) and the Caregiver-Teacher Report Form (C-TRF), are usable by many different kinds of professionals in diverse settings. The CBCL/1.5-5 also includes the Language Development Survey (LDS), which provides a quick screen for delays in vocabulary and word combinations. The problem items of the CBCL/1.5-5 and the C-TRF are scored on both empirically based syndromes and DSM-oriented scales, which are normed on the same general population sample. Variations in children's functioning across contexts and interaction partners make it essential to obtain and integrate data from multiple sources. Therefore, ASEBA software provides side-by-side comparisons of item and scale scores from up to eight assessment forms per child. Clinical and research applications of ASEBA preschool forms are summarized in the paper, and strengths and limitations are discussed. (Contains 4 figures.)