Most school curricula include the study of health as a separate subject or as part of science. Despite this, students often leave school without a clear understanding of many health concepts. This study investigated a group of grade eight and nine students' knowledge of personal health and physical fitness concepts and its relation to locus of control. A 20 item true-false knowledge questionnaire with opportunities for students to explain their choice indicated that while students scored relatively well on the items the explanations of their responses frequently indicated erroneous reasoning based on preconceptions or misconceptions. Students' locus of control was measured using two instruments for health and fitness respectively and showed that this sample had a higher expectation of control by themselves for their fitness compared to their health. Correlation data between knowledge and locus of control scores indicated that students who possessed high knowledge scores had a tendency not to believe in chance for their personal health and physical fitness. Conversely students who possessed low knowledge scores had more of a tendency to believe in chance for their personal health and physical fitness. The study comments on the success of the health education curriculum and offers suggestions for further research. (Author)