The purpose of this study was to identify prospective primary school teachers' misconceptions about the states of matter. The sample of the study was 227 fourth-year prospective primary school teachers in a Department of Primary Education in Turkey. Researcher asked from every participant to write a response to an open ended question about differences among solid, liquid and gaseous states of matter. In analyzing the research data, the researcher used descriptive analysis techniques. The findings of the research indicated that prospective primary school teachers have some misconceptions such as: The shape of solids do not change, there is no space between the particles of solids, since gases are not affected by gravity they do not fall down like the solids and liquids, the size of the particles of solids is bigger than the particles of liquids, and the particles of liquids are bigger than the ones of gases. (Contains 1 table.)