This study identifies and describes students’ mathematical reasoning, when students work with probability tasks. The study also, to some extent, examines the role of oral communication in mathematical classrooms. The students who participated in the study were all in grade 9, the last year of the compulsory school in Sweden. The students were videotaped during their work with the probability tasks and their conversations were transcribed. The tasks are chosen with the purpose to engender oral communication and discussions concerning probability. A practical epistemology analysis was conducted on the data. The observed students’ reasoning concerning probability was analyzed and compared with reasoning competencies and framework for mathematical reasoning. Students’ reasoning was also examined in relation to sociomathematical norms and students’ aesthetic judgments were analyzed.