As the technologies in the field of education are becoming more and more sophisticated, continuous professional development for teachers is gaining increasing importance. Therefore, teachers need to improve themselves to grow more competent professionally, to adapt to innovations in their field and to be aware of their competencies throughout their professional careers. A support for professional development can be given to teachers through inservice training programs or mentoring practices. This study aims to improve chemistry teachers' adaptation to the renewed curriculum with a group mentoring program and to determine the effects of this program on professional development of teachers by individually and as a group. The study group consists of four (three males, one female) chemistry teachers working in the central districts of the province of Trabzon in Turkey. A Course Evaluation Form developed by the researchers was used to examine the effect of the teachers' mentoring support experiences on their classroom practices. Each teacher was observed before, during and after the mentoring. Every one of the classroom teaching practices was video-recorded. The video recordings were analyzed according to the themes and codes in the course evaluation form. The findings show that there is a change in teachers' in-class practices before, during and after the mentoring, and while this change shows continuous improvement in some cases, it is variable or stationary in some others. [ABSTRACT FROM AUTHOR]