This study investigated participation in a state-level science competition over most of its 35-year history. Issues examined included whether different gender patterns occurred with respect to entry rate, project topic (life science, physical science, earth science, and math), and project type (research or display). The study also examined to what extent the identified patterns reflected or contradicted nationwide patterns of girls' academic performance in science over roughly the same time period. It was found that although girls initially participated in the fair less frequently than boys, for the past 20 years their participation rate has been greater than that of boys. Examination of topic preferences over the years indicates that both girls and boys have traditionally favored life science; however, boys have been and continue to be more likely to prepare physical, earth, and math/computer science projects than girls. Another gender difference is that girls are generally less likely than boys to prepare projects based on experimental research as opposed to library research. The study provides some suggestions for teachers and teacher educators for addressing these disparities.