The results are described of two case studies on the conceptions and classroom practice of two Portuguese physics and chemistry teachers on the role of problem solving in the teaching/learning of science. One of these teachers was a novice and the other had about 20 years of teaching experience. The data were obtained from a questionnaire, a semi-structured interview, classroom observation, personal documents, and stimulated recall. The analysis was carried out with instruments organised into categories and specific indicators. The results showed there to be major differences between the intention behind the new curricula, the teachers' conceptions, and their practice. Some suggestions are put forward on the basis of these results for the initial and ongoing education of secondary education teachers of physics and chemistry in Portugal.