The aim of this study was to investigate the development of student teachers' skills in preparing and using overhead transparencies (OHTs) through micro-teaching activities. The study was carried out with 48 student teachers in the Primary Science Teacher Education Program of the Fatih Faculty of Education at Karadeniz Technical University during the 2007-2008 academic year. After being split into groups, the student teachers were instructed to prepare OHTs on predetermined science curriculum topics. Groups were required to give 10-minute presentations. Their presentations were recorded using a video camera. The study revealed that the student teachers' skills in using drawings, arranging relationship between headings and text, providing figure-text interpretation and presenting stimuli in question form were improved. They also showed better skills in delivering the subject matter. It is recommended that process-based skills of student teachers be developed by giving more attention to micro-teaching activities.