Teacher certification program raises a question of whether certified teachers really more competence than non-certified teachers. However, since the notion of teachers’ competence is measure in terms of content knowledge and pedagogical knowledge instead of Pedagogical Content Knowledge (PCK). Teacher’ PCK as the essence of teachers’ competence is somehow ignored. The study presented here analyses experienced biology teachers’ PCK. Subjects are experienced biology teachers who teach at the formerly called Pioneered Standardized Schools (RSBI). They are purposively chosen since they are certified teachers who have received very intensive training organized by the education authorities (national, province and district) as well as by the schools. Therefore, this group of teachers can be considered as experienced and well-prepared for teaching science.