In this study, the errors and the confusions of the pre-service science teachers on the subject of fermentation have been researched; and it has been found out that fermentation concept is mostly confused with the concept of respiration. The conception between the two concepts is a period which starts from science and technology courses in primary schools and lasts till university education. The study has 2 levels. In first level, some definitions and concepts from the course books studied in science and technology courses of 4.-8. grades in primary school, in high school biology courses and in university biology courses were examined. Second level was carried out with the participation of 85 pre-service science teachers from istanbul University, Hasan Ali Yucel Education Faculty, Department of science education. A questionnaire was applied to be able to understand whether the misconceptions between the concepts of respiration and fermentation, coming from primary school and high school, continued during university education or not. SPSS 13.0 program was used to analyze the results. At the stage of data evaluation, Chi-Square test technics was used. All results were evaluated, discussed and suggestions were brought forward.