Journal of Abnormal Child Psychology, Vol. 31, No. 5, October 2003, pp. 495–514 ( C  2003) The Infant–Toddler Social and Emotional Assessment (ITSEA): Factor Structure, Reliability, and Validity Alice S. Carter, 1,4 Margaret J. Briggs-Gowan, 2 Stephanie M. Jones, 2 and Todd D. Little 3 Received June 12, 2001; revision received November 4, 2002; accepted November 20, 2002 In this paper the refinement and psychometric properties of the Infant–Toddler Social and Emotional Assessment (ITSEA) are described. Results from a sociodemographically diverse birth cohort sample of 1,235 parents of children between the ages of 12 and 36 months are presented. Confirmatory factor analyses supported the hypothesized Internalizing, Externalizing, Regulatory, and Competence do- mains as well as the 17 individual scales that comprise the ITSEA. Findings for 3 additional indices useful in identifying significant psychopathology are presented. Subgroup analyses revealed structural invariance and expected mean level differences across both child sex and 6-month age bands. Child sex differences emerged for some problem and most competence scales, with boys rated as higher on Activity/Impulsivity and girls rated higher on Anxiety and most Competence scales. All competence scores increased across age groups. Problem behaviors showed a more mixed developmental pattern. Test–retest and interrater reliability were acceptable. Associations between the ITSEA and indepen- dent evaluator ratings and parental ratings of child behavior problems, temperament, and parental distress support the validity of the instrument. KEY WORDS: behavior problems; social–emotional competencies; infant; assessment; scale development. In this paper, the refinement of a recently developed comprehensive adult-report measure of social–emotional problems and competencies in 1- to 3-year-olds, the Infant–Toddler Social and Emotional Assessment (ITSEA), is presented. Until recently, the assessment of very young children’s problem behaviors and competen- cies has been constrained by a lack of age-appropriate in- struments. Although systematic study of social–emotional problems and competencies in a normative context was compromised by the lack of age-appropriate instruments, clinical observations and empirical studies of at-risk chil- dren have documented the presence of serious and per- sistent social–emotional problems in infants and toddlers (Radke-Yarrow, Nottelmann, Martinez, Fox, & Belmont, 1 Department of Psychology, University of Massachusetts Boston, Boston, Massachusetts. 2 Yale University, New Haven, Connecticut. 3 University of Kansas, Lawrence, Kansas. 4 Address all correspondence to Alice S. Carter, PhD, De- partment of Psychology, University of Massachusetts Boston, 100 Morrissey Boulevard, Boston, Massachusetts 02125; e-mail: alice.carter@umb.edu. 1992; Sameroff & Emde, 1989; Zeanah, 2000; Zero to Three, 1994). Moreover, many of these early problems have shown remarkable stability into the school-age years (Campbell & Ewing, 1990; Fischer, Rolf, Hasazi, & Cummings, 1984; Prior, Smart, Sanson, Pedlow, & Oberklaid, 1992; Shaw, Keenan, & Vondra, 1994). Normative data for problem behaviors are available for children from 2- to 3-years of age (Achenbach, Edelbrock, & Howell, 1987; Briggs-Gowan, Carter, Skuban, & Horwitz, 2001; Prior et al., 1992; Richman, Stevenson, & Graham, 1982; Thompson et al., 1996) and more recently for children as young as 18 months of age (Achenbach & Rescorla, 2000; Mathiesen & Sanson, 2000). However, to fully understand the social–emotional development of infants and toddlers, it is critical to assess social–emotional and behavioral competencies as well as problems. Competence in stage salient tasks increases the likelihood of later competence and likely minimizes the emergence and maintenance of maladaptive patterns. In contrast, lags in social–emotional competence will likely increase risk for subsequent social–emotional and behav- ioral problems (Carter, 2002; Cicchetti & Cohen, 1995; 495 0091-0627/03/1000-0495/0 C  2003 Plenum Publishing Corporation