The purpose of this study was to examine the psychometric properties of the "Autism Program Environment Rating Scale" ("APERS"), an instrument designed to assess quality of program environments for students with autism spectrum disorder. Data sets from two samples of public school programs that provided services to children and youth with autism spectrum disorder were utilized. Cronbach alpha analyses indicated high coefficients of internal consistency for the total "APERS" and moderate levels for item domains for the first data set, which was replicated with the second data set. A factor analysis of the first data set indicated that all domain scores loaded on one main factor, in alignment with the conceptual model, with this finding being replicated in the second data set. Also, the "APERS" was sensitive to changes resulting from a professional development program designed to promote program quality.