Despite the current legislation requiring sex education as part of the school curriculum in Portugal, great obstacles to its implementation remain. Furthermore, sex education is far from being systematically administered. Thus, the main interest in our project was to validate a scale that measures teachers' attitudes towards sex education. There are to date no scales in the literature, with tested psychometric characteristics, that achieve this objective. Hence in this work we constructed the Sex Education Teachers' Attitudes Evaluation Questionnaire and we proceeded to validate it. This questionnaire also includes a scale of knowledge of sex education and one of comfort with the themes of sexuality. The 176 individuals who participated in this research are teachers from the second and third basic educational levels and from high school. The scales revealed great consistency and adequate validity. (Contains 7 tables.)