Computer technology in mathematics education enabled the students find many opportunities for investigating mathematical relationships, hypothesizing, and making generalizations. These opportunities were provided to pre-service teachers through a faculty course. At the end of the course, the teachers were assigned project tasks involving investigation and discovery activities. This paper presents the mathematical thinking processes and pre-service teachers' experiences in the course of investigation and discovery activities. The pre-service teachers claimed that they learned new mathematical concepts, as also how to apply their mathematical knowledge. Finally, some useful examples of the mathematical processes experienced by the students during their project work are presented. (Contains 1 table and 11 figures.)