The purposes of this study were to determine the impact of a professional development program on the confidence levels and classroom practices of the participants and their attitudes toward the environment. The program had immersed teachers in a watershed study that took them from the headwaters of a 310-mile river to its confluence with the Ohio River over a 6-day period during the summer. The teaching approaches used were based on national standards, best teaching practices, and current trends in environmental education. Pre-, post-, and long-term postsurvey data were analyzed using a MANOVA and univariate tests to measure changes in confidence levels and classroom practices in the use of various technology; standards-based teaching strategies; community resources; field investigations; and in the teaching of watershed topics, real life topics, societal issues, and career education. The results of a separate pre-, post-, and long-term postsurvey were analyzed using a paired samples t test to measure changes in teachers' environmental attitudes. Recommendations are presented that can be generalized across a variety of educational programs. (Contains 11 tables.)