Students' attitudes toward chemistry lessons in school are important dependent variables in curriculum evaluation. Although a variety of instruments have been developed by researchers to evaluate student attitudes, they are plagued with problems such as the lack of theoretical rationale and of empirical evidence to support the construct validity of data. This paper describes a study of students' attitudes toward chemistry lessons in Hong Kong secondary schools. One of the scales in the Test of Science-Related Attitudes developed by Fraser was modified to form an Attitude Toward Chemistry Lessons Scale (ATCLS). The construction of the ATCLS was based on a theoretical model with four dimensions: liking for chemistry theory lessons, liking for chemistry laboratory work, evaluative beliefs about school chemistry, and behavioural tendencies to learn chemistry. The arguments for inclusion of these four dimensions are presented. The final version of ATCLS was administered to 954 students. The results of confirmatory factor analysis indicated that there was a good fit between the hypothesised model and the observed data. (Contains 1 figure and 5 tables.)