This Spanish contribution to the STTIS (Science Teacher Training in an Information Society) investigations of transformations of curriculum innovations studies the implementation of a particular innovative teaching sequence on energy degradation in Spanish secondary schools. The paper describes the transformations found in teachers' interpretations of the rationale for the teaching sequence that could give rise to alternative conceptions about energy degradation and related concepts in students. Research-based teacher education materials aimed at overcoming some of the difficulties encountered have been developed. The materials rely on the idea of a learning cycle to facilitate changes in teachers' conceptual understandings, through co-operative work and through reflection on practice. © 2004 Wiley Periodicals, Inc.