With the existing shortage of qualified high school physics teachers and the current mandate of the No Child Left Behind Act requiring teachers to be "highly qualified" in all subjects they teach, university physics departments must offer content courses and programs that would allow out-of-field high school physics teachers to meet this requirement. This paper will identify how the University of Northern Iowa Physics Department is attempting to address the needs of the high school physics teacher through its course offerings and professional development programs for teachers. The effectiveness of one such physics professional development program, the UNI Physics Institute (UNI-PI), on secondary science teachers' and their students' conceptual understanding of Newtonian mechanics, and the teachers' instructional practices was investigated. Twenty-one Iowa out-of-field high school physics teachers participating in the program were able to complete the physics coursework required to obtain the State of Iowa 7–12 Grade Physics Teaching endorsement. Twelve of the participants completed a two-year program during the 2002 and 2003 summers. Background information, pre- and post-test physics conceptual assessments and other data was collected from participants throughout the Institute. Participants collected pre and post-test conceptual assessment data from their students during the 2002–2003 and 2003–2004 academic years. This comprehensive assessment data revealed the Institute's influence on participants' and students' conceptual understanding of Newtonian Mechanics. The results of this investigation, the insights we have gained, and possible future directions for professional development will be shared.