This study investigated Biology teachers' knowledge and practices of performance assessment introduced with the recent curriculum reform in Turkey. Data for the study was collected through a questionnaire and in dept interviews with 22 Biology teachers working at secondary schools from both rural and urban areas of Trabzon, Turkey. According to the findings, changes introduced regarding the assessment system with the new curriculum have not entered the classrooms yet, mainly because of the lack of knowledge and skills of teachers. Suggestions to better equip teachers with the requirements of the changes, through provision of appropriate training and experiences for conceptual change, were included at the end of the paper. (C) 2010 Elsevier Ltd. All rights reserved.