The effect of a professional development program on the quality of care provided for infants and toddlers was assessed with a sample of 160 caregivers in 96 infant?toddler rooms in 48 childcare programs. Caregivers participated in a 3-month training course with a standardized curriculum of five 3-hour group classes and an out-of-class project. A total of 123 participants in 70 classrooms also received onsite consultation. Consultation was not provided for 37 participants in 26 classrooms. The effect of training program participation was judged using pre- and posttraining comparisons between mean total scale scores on the Infant/Toddler Environment Rating Scale (Harms, Clifford, & Cryer, 1990) Comparisons also were made between classrooms where score differences were rated as observable change. Observable change was evident in 15 (21.4%) infant?toddler rooms in the consultation group, in comparison to 2 (7.7%) infant?toddler rooms in the no-consultation group.