This study explored the factor structure of Darkenwald and Valentine's Adult Classroom Environment Scale (ACES). The Student Ideal form of the ACES was administered to 449 adult students from a variety of educational settings and a factor analysis was performed. All but 15 of the original 49 items loaded clearly with a five-factor orthogonal solution, which only partially supported the seven dimensions proposed by Darkenwald and Valentine. A revised version of the scale was then administered to an additional 287 adult students. A second factor analysis largely confirmed the stability of the five factor solution, although a tentative sixth factor was identified.