As part of the Calculators in Primary Mathematics project, seven infant teachers taking part in a long-term investigation into the effects of the introduction of calculators on the learning and teaching of primary mathematics, were observed in their classrooms and interviewed over a period of three years. One of the original hypotheses of the project was that teachers would adopt a more open-ended teaching style as a result of the increased opportunities for exploration of number presented by the calculator. It was also hypothesised that the presence of the calculator would extend the range of problem solving activities in the classroom. All seven teachers, at some stage of their involvement in the project, claimed to have become more open- ended in their teaching, with the majority stating that their mathematics teaching had become more like their language teaching. Two teachers reported a less open-ended approach in their second year of involvement compared to their first year Ð mainly due to a perceived need to instruct children on calculator use. A majority of teachers also claimed there was more sharing and discussion in their classrooms, which some identified as providing opportunities for observations of children, leading to catering better for the full ability range. An increase in problem solving activity, often related to the real world, was identified as a change by four teachers. None of these claims were contradicted by the classroom observations.