Two studies examined developmental outcomes associated with services in inclusive and self-contained preschool classrooms. In Study 1, the effects of classroom inclusion on the developmental and social growth of preschool children with disabilities were investigated on 15 pairs of children (N = 30) matched for chronological age, gender, initial level of functioning, related services received, and attendance schedules. Progress was measured with the Brigance Diagnostic Inventory of Early Development-Revised using a pre-post design. Results indicated that children functioning at a lower level of social and emotional functioning performed equally well in inclusive and specialized settings, while children functioning at a relatively higher level performed better in inclusive settings than in specialized settings. In Study 2, the relationships between developmental progress and the length of the school day and the amount of related services received per week were investigated on 66 participants. Children in full-day classrooms had greater developmental delays but achieved higher rates of progress than their half-day peers in the areas of social and emotional development and overall development.