Decimals are among the difficult subjects for the students because of its abstract nature. Therefore, the aim of this study is to develop instructional materials for students based on one of the four-stage models of constructivist approach related to the unit of "decimals". With this aim, a worksheet, analogy map and conceptual change text on the unit of decimals were developed. Case study method was used in the study. A pilot study was conducted with 32 6(th) graders studying in an elementary school in Trabzon in order to use the instructional materials in the classes more effectively and to test their feasibility. At the end of this preliminary study, the students were determined to find the materials effective, visual and interesting. Therefore, it's recommended to use the materials developed during the course in mathematics classes and to develop similar materials for other subject matters. (c) 2010 Elsevier Ltd. All rights reserved.