This study had two goals. The first was to validate further Sternberg's theory of mental self-government in a cross-cultural setting. The second was to investigate the relationship between thinking styles and teachers' characteristics. Research participants were one hundred ninety-three (65 male and 128 female) in-service teachers studying in the Bachelor of Education degree program and the Postgraduate Certificate in Education program at the University of Hong Kong. The participants responded to the Chinese version of the Thinking Styles Questionnaire for Teachers (TSQT) that has its theoretical foundation in Sternberg's theory of mental self-government. They also provided a range of demographic information such as age, gender, family income, and duration of their teaching experience. Furthermore, they rated themselves on a 5-point Likert scale about their teaching practices and about their perceptions of their school environment. The results of the study showed that the TSQT is a reliable and valid inventory for assessing the thinking styles of primary and secondary school in-service teachers in Hong Kong. Cronbach's alphas ranged from .58 to .75, with a mean of .68 and a median of .66. A principal-axis factor analysis followed by an oblique rotation resulted in two factors that accounted for 73.8% of the variance in the data. Moreover, results from stepwise multiple-regression procedures indicated that six characteristics of teachers were significantly correlated with the thinking styles specified by the theory of mental self-government. These teacher characteristics are gender, professional work experience outside school settings, the degree of enjoying adopting new teaching materials, a tendency for using group projects in assessing student achievement, perceived autonomy for determining their teaching contents, and their rating of the quality of their students. We discussed seven possibilities for using the knowledge about thinking styles to facilitate an enhancement