In science teaching insufficient emphasis is placed on the fact that models are simulations of reality based on a certain theory and that molecules are not miniatures of the models that represent them. The study reported in this paper investigated how chemistry teachers perceive the nature and functions of models. The research population included an experimental group of in-service teachers who attended a 56 hour training and a control group of pre- and in-service teachers. The training dealt with the model concept and ways to use various model types to illustrate chemical bonding and structure. Results indicate that: most of the participants thought of a model as a way to describe a process or a phenomena which we cannot see, they perceived models as a means to enlarge or reduce real processes or phenomena or to illustrate some theory, more teachers who took part in the training agreed that models can be used for prediction, and only teachers of the experimental group made a distinction between a mental image and a concrete model that can be seen and touched. It was concluded that the in-service training on models improved several aspects of the trainees' model perception. Contains four references. (Author/JRH)