This dissertation used a combination of case study and phenomenological research methods to investigate how individual teachers of middle school science in the Alabama Math, Science, and Technology Initiative (AMSTI) program sustain their use of inquiry-based methods of teaching and learning. While the overall context for the cases was the AMSTI program, each of the four teacher participants in this study had a unique, individual context as well. The researcher collected data through a series of interviews, multiple-day observations, and curricular materials. The interview data was analyzed to develop a textural, structural, and composite description of the phenomenon. The Reformed Teaching Observation Protocol (RTOP) was used along with the Assesing Inquiry Potential (AIP) questionnaire to determine the level of inquiry-based instruction occuring in the participants classrooms. Analysis of the RTOP data and AIP data indicated all of the participants utilized inquiry-based methods in their classrooms during their observed lessons. The AIP data also indicated the level of inquiry in the AMSTI curricular materials utilized by the participants during the observations was structured inquiry. The findings from the interview data suggested the ability of the participants to sustain their use of structured inquiry was influenced by their experiences with, beliefs about, and understandings of inquiry. This study contributed to the literature by supporting existing studies regarding the influence of teachers' experiences, beliefs, and understandings of inquiry on their classroom practices. The inquiry approach stressed in current reforms in science education targets content knowledge, skills, and processes needed in a future scientifically literate citizenry.