This study investigated the effects of teaching basic math skills to 16 children (11 typically developing, 5 with developmental delays) in an integrated university preschool. "Connecting Math Concepts Level K (CMC--K"; Engelmann & Becker, 1995) was delivered by the classroom teacher to small groups of 4 to 6 children over 6.5 weeks. All children were pre- and posttested using the Cognitive Domain of the Battelle Developmental Inventory (BDI) and the placement test for "Connecting Math Concepts Level A (CMC--A"; Engelmann, Carnine, Kelly, & Engelmann, 1996). Results of the BDI showed a Cognitive Domain effect size of 0.61 for typically developing children (subdomains ranged from 0.05 to 0.87). Children with developmental delays had a Cognitive Domain effect size of 0.54 (subdomains ranged from 0.38 to 1.59). On the "CMC--A" placement test, typically developing children had a mean pretest score of 4.55 and a mean posttest score of 7.90. Those children with developmental delays had a mean pretest score of 3.80 and a mean posttest score of 7.20. Implications for future research are discussed. (Contains 1 table.)