This article reports on information disseminated and discussions and recommendations elaborated in the theme group on "Technology and Cognitive Development" at the Fifth International Congress on Mathematical Education (ICME 5) which took place in Adelaide, Australia, August 1984. In a four-session working program, the group focused on three questions around which this report is organized: 1. The use of technology to further the cognitive development of learners of mathematics; 2. The use of technology to achieve a better understanding of the processes involved in the development of children's cognitive structures relevant to mathematics; 3. Possible disadvantages connected with the use of technology.