Secondary science teachers play an important role in forming the imagt: of science that is held by theirpupils. However, research suggests that quite often science teachers' conceptions of thr: nature of scientific knowledge are little better that of their students. In Portugal, there are no research studies which may help to characterise science teacher's epistemological views in order to design appropriate training courses. 'This study aims (I) to diagnose what conceptions (empirist/rationalistic) are held by Portuguese secondary science teacliers concerning the relationship between theory and observation and also about the called scientific method (II) to anaiyse the relationship between such conceptions, and the variables subject matter taught and professional experience. Basic data was generated from responses to a questionnaire (multiple choice questions) given by a representative sacnple of 464 science teachers. The results showed the predominance of empirist views (nearly 2/3 of the sample) about the two aspects investigated. Empirist views seem to be independent of the teaching subject and professional experierice. The need for adequate training courses is discussed and siíggestions concerning their design are proposed.