The article includes part of a research study on experimental work in teaching science (Santos, 2002): a teacher with ten years in the profession received teacher training. It goes on to describe the training programme, which lasted six months and is included in the practice-oriented training paradigm (Kennedy, 1987), along with a reflective approach to practice (Gomez, 1992). The goal of this training was the teacher's professional development. The article also includes the teacher's own reflections, immediately after completing training and four years later.