The assessment of social-emotional and adaptive behavior functioning is critical during the preschool years because many of these affective and skill-related areas form a foundation that guides and influences children's later functioning in home, school, and community domains. Ongoing assessment in these areas is able to identify children's age-appropriate development or their atypical development in one or a number of areas. From a social-emotional perspective, atypical development may involve anxiety disorders, attachment disorders, or pervasive developmental disorders. From a behavioral or functional perspective, atypical development may involve skill deficits, performance deficits, or deficits of self-control or self-management. In total, the assessment process attempts to integrate all of these perspectives while evaluating the child in an objective and ecological context. This context is discussed briefly first because of its importance to accurate, effective assessment. The chapter then provides specific information on direct observation, clinical interviews, behavior rating scales, behavioral observation approaches, projective techniques, and adaptive behavior scales.