The Hong Kong Classroom Environment Scale (HKCES) is a new instrument designed to assess upper primary and junior secondary school students' perceptions of actual and preferred classroom environment. The development of the scale involved 2 stages of study. In the 1st stage of study, exploratory and confirmatory factor analyses clearly identified 4 dimensions of classroom environment: teacher involvement, teacher support, order and student involvement and collaborativeness. In the 2nd stage of study, the instrument was administered to a new sample of about 6,000 students from 13 primary schools and 5 secondary schools for cross-validation. (Contains 12 tables and 1 figure.)