One of the most important attribute for being scientifically literate in the context of science education requires individuals do research, inquiry and develop scientific attitudes toward facts brought about around them. In addition, it is often stated in the literature that individuals who are scientifically literate can also think critically and possess certain skills of critical thinking. According to previous research, the frequency of using critical thinking skills is interconnected to tendency of using critical thinking dispositions. Critical thinking dispositions are developed and changed on the basis of social environments and the relationship between these environments. The purpose of this study is twofold. The first one is to determine the critical thinking dispositions of preservice science teachers and the second one is to examine the possible effects of some variables including personal and social factors. The study included 346 preservice science teachers from three universities located in the distinct parts of Turkey. The study was designed in accordance with descriptive survey method. Data were collected through California Critical Thinking Disposition Inventory (CCTDI). ANOVA, independent samples t-test and tukey test are used in the analysis of the data. The results of the study revealed that preservice science teachers' critical thinking dispositions is low. In addition, there is not a significant difference between preservice science teachers' critical thinking dispositions scores by gender, grade, school and authority at home variables whereas there is by other variables such as decision making independently and receiving academic guidance. [Paper presented at the Congress of Educational Sciences (22nd, Eskisehir, Turkey, September 5-7, 2013).]