The aim was to determine whether ratings of 2- and 3-year-olds could yield more differentiation among their behavioral/emotional problems than the internalizing-externalizing dichotomy found in previous studies. The 99-item Child Behavior Checklist for Ages 2-3 (CBCL/2-3) was designed to extend previously developed empirically based assessment procedures to 2-and 3-year-olds. Factor analyses of the CBCL/2-3 completed by parents of 398 2- and 3-year-olds yielded six syndromes having at least eight items loading greater than or equal to .30 and designated as Social Withdrawal, Depressed, Sleep Problems, Somatic Problems, Aggressive, and Destructive. Second-order analyses showed that the first two were related to a broad-band internalizing grouping, whereas the last two were related to a broad-band externalizing grouping. Scales for the six syndromes, two broad-band groupings, and total problem score were constructed from scores obtained by 273 children in a general population sample. Mean test-retest reliability r was .87, 1-year stability r was .69, 1-year predictive r with CBCL/4-16 scales at age 4 was .63, 2-year predictive r was .55, and 3-year predictive r was .49. Children referred for mental health services scored significantly higher than nonreferred children on all scales. A lack of significant r's with the Minnesota Child Development Inventory, Bayley, and McCarthy indicate that the CBCL/2-3 taps behavioral/emotional problems independently of the developmental variance tapped by these measures.