According to the aims of the current junior science curriculum for Hong Kong, students are expected to master inquiry skills for problem-solving, understand the nature of scientific knowledge, and appreciate the limitations of science. These aims are, however, difficult to achieve because available science textbooks focus mainly on the transmission of scientific facts and concepts and most science teachers do not have a good understanding of the nature of science. In order to improve this situation, the Integrated Science course of the Postgraduate Diploma in Education Program of the Faculty of Education, the Chinese University of Hong Kong, has in recent years incorporated a unit that aims at facilitating teachers to construct understanding of the nature of science. This article reports a small-scale study of the effect of this unit on a group of in-service science teachers. The unit consists of a number of historical vignettes that illustrate the process of development of scientific ideas, through which teachers were guided to construct the key steps of the scientific methods and appreciate the nature of scientific knowledge. A pre-test was administered to the subjects to identify their alternative conceptions on the nature of science. Comparison of the scores of the pre-test and post-test indicates that the subjects were found to demonstrate substantial improvement in their understanding of the nature of science after intervention, but some alternative conceptions were still persistent in most subjects. Implications were made for ways to integrate the historical approach into science teaching in schools. (Contains 1 table and 3 figures.)