This study sought to measure general teacher efficacy levels of in-service primary teachers in Hong Kong. Participants included 725 Hong Kong in-service teachers, who were invited to take part in the study. These in-service teachers came from 28 different primary schools ranging from government, aided, private and direct subsidy schools. The Chinese version of the 12-item Teachers' Sense of Efficacy (C-TSE) Scale was applied to investigate the efficacy of the teachers. A factor analysis of these 12 items when male and female datasets were combined led to the extraction of only one factor. But separation of the two datasets led to the extraction of different factor analysis models. This could reflect the different perceptions that male and female teachers had about the formation of teacher efficacy. Overall, this study showed that female teachers were significantly more efficacious than male teachers. Moreover, years of teaching experience showed a weak but significant correlation to levels of general teacher efficacy. Interestingly, educational levels did not have a significant effect on the efficacy of this group of in-service primary teachers. Overall, the C-TSE was found to be a valid and reliable scale for measuring the efficacy levels of this particular group of in-service primary teachers in Hong Kong. [Copyright of Journal of Education for Teaching is the property of Routledge. Full article may be available at the publisher's website: http://dx.doi.org/10.1080/02607470600982134]