The aim of this study is to reveal the perceptions of preservice mathematics teachers on the concepts of infinity, indeterminate and undefined. The study was conducted with 83 teacher candidates attending to Primary School Mathematics Education at a state-owned university. A two-part test was applied to preservice teachers. In the first part of the test, three questions were directly posed to preservice teachers to clarify what they understand the concepts of infinity, indeterminate, and

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... ed. In the second part of the test, nine cases representing infinity, indeterminate and undefined (∞+∞, 1∞ and 1/0 etc.) were given to the teacher candidates and they were asked to explain what these symbolic representations mean to them. Based on the data obtained from the test, the candidate teachers (23%) has been more successful in explaining the concept of indeterminate. Except for the concept of undefined, their daily life experiences were seem to be effective to their explanations about the other two concepts. It was also determined that preservice teachers substitute these three concepts to each other. Besides, the study concluded that previously learned some dominant rules were quite effective to teacher' candidates' decisions of the about given symbolical cases. Summary Purpose and Significance An extensive review of the literature revealed that most of the various grade level students have difficulty in understanding the concepts of infinity and undefined. A review of literature also showed that there is limited studies conducted about the concept of indeterminate. Since these concepts are vitally important in comprehending the basic and advanced mathematical topics (limit, continuity, derivative, integral etc.), researches on teachers' and preservice teachers' perception of these concepts are essential. The aim of this study is to reveal the pre-service mathematics teachers' perceptions about the concepts of infinity, indeterminate and undefined. Method This study was conducted with 83 teacher candidates studying Primary School Mathematics Education at a state-owned university, Turkey. A two-part test was developed to reveal pre-service teachers' perception on the concepts of infinity, indeterminate, and undefined. In the first part of the test, three questions were directly posed to pre-service teachers to clarify what they understand the concepts of infinity, indeterminate, and undefined. In the second part of the test, nine cases representing infinity, indeterminate and undefined (∞+∞, 1∞ and 1/0 etc.) were given to the teacher candidates and they were asked to explain what these symbolic representations mean to them. Content analysis was used to analyze teacher candidates' responses.