The self-efficacy beliefs of in-service elementary school teachers in Greece were examined in an attempt to evaluate their biology teaching skills. For this purpose, we constructed a valid and reliable instrument consisting of a Likert-type questionnaire that was distributed to the target population and to which 202 teachers responded. Results revealed Greek primary education teachers have, in general, moderate to high biology teaching self-efficacy beliefs (BioTSEB), whereas those that had not attended any biology courses during their academic studies had lower self-estimates. Teachers' BioTSEB are also affected by factors such as years of teaching experience, the number of science courses attended and the quality of their previous studies, together with the grade levels they were assigned to teach during their in-service years. (Contains 3 tables.)