Our work is based on two premises. The first is that affective factors (beliefs, attitudes, and emotions) influence teaching and learning mathematics, and problem solving in particular. The second is that initial teacher education is an important element in the process of improving overall educational practice. On this basis, our research group has been working on evaluating the influence of affect in mathematics problem solving for prospective teachers, and on designing and implementing a program of metacognitive intervention that integrates cognitive and affective factors. The present communication describes our research in this line. (Contains 11 figures, 5 tables and 1 footnote.)