We compare the content that was expected with what actually was put into practice in a course of ongoing education of secondary education (12-16 year olds) science teachers, and describe the most relevant problems that arose. We believe that the educational content--its nature, how it is organized and presented to the teacher participants, and so on--has a major influence on the relationships that are established between 'theory' and 'practice'. It is from this perspective that the results are analysed. The data come from statements made by those involved--the director and the coordinator of the course and the teacher participants--obtained in interviews and written documents. The inference drawn from the analysis of the results is that, in the educational strategy that was being studied, practice is not conceived of as a genuine scenario of production of meanings, but only as a field of application of the theories of the disciplines being taught. This has a decisive influence on the development of the course and on the degree of professional evolution of the participants.