This study examined differences in classroom quality, assessed by the Infant/Toddler Environment Rating Scale-Revised (ITERS-R), in 287 infant and 479 toddler classrooms. Classroom quality was compared across classroom age group (infant compared to toddler classrooms) as well as across programme type (for-profit compared to not-for-profit programmes). Classroom quality was assessed using four ITERS-R factors identified in previous research, including Materials/Activities, Safety/Organization, Language/Interactions, and Parents/Staff factor scores. Results indicate that infant classrooms scored higher on the Safety/Organization and Language/Interactions factors than toddler classrooms, and toddler classrooms scored higher on Materials/Activities than infant classrooms. Classrooms in not-for-profit programmes scored higher on Safety/Organization and Parents/Staff factors. Differences in Safety/Organization, Language/Interactions, and Parents/Staff factor scores were found based on teachers' education, and teachers' experience in the programme was positively related to scores on the Language/Interactions factor. Implications regarding the provision of high-quality classroom environments for infants and toddlers in both programme types are discussed. (author abstact)