Despite the positive outcomes for inquiry-based science education and recommendations from national and state standards, many teachers continue to rely upon more traditional methods of instruction This causal-comparative study was designed to determine the effects of the Inquiry Institute, a professional development program that is intended to strengthen science teachers' pedagogical knowledge and provide practice with inquiry methods based from a constructivist approach. This study will provide a understanding of a cause and effect relationship within three levels of the independent variable-length of participation in the Inquiry Institute (zero, three, or six days)-to determine whether or not the three groups differ on the dependent variables-beliefs, implementation, and barriers. Quantitative data were collected with the Science Inquiry Survey, a researcher-developed instrument designed to also ascertain qualitative information with the use of open-ended survey items. One-way ANOVAs were applied to the data to test for a significant difference in the means of the three groups. The findings of this study indicate that lengthier professional development in the Inquiry Institute holds the most benefits for the participants.