This study examined some long-term impacts of a professional development program, Teachers in the Woods. Several outcomes of the program were acknowledged by participants as having been valuable: a network of like-minded teachers, a network of scientists and teachers, and an increase in teachers' ecological knowledge and field skills. The authors made 3 observations with regard to professional development. First, engaging teachers in real-world field science research is an effective way for them to gain ecological knowledge and skills. Second, the collegiality among teachers and scientists developed during the period of field work can enhance science learning. Third, collegiality among teachers provides opportunities to discuss pedagogy-related issues. Both aspects of collegiality provide support mechanisms that sustain teachers' efforts to modify their teaching practices.