This study analyzes the citations included in forestry master's theses at Mississippi State University from 1999 to 2003 in order to increase librarians' understanding of the sources used by forestry researchers. The results, which are compared with related citation studies, demonstrate the interdisciplinary nature of the field as well as the variety of sources used in forestry research. Forestry graduate students cited journal articles, books, theses and dissertations, conference proceedings, government and university publications, association and company reports, and miscellaneous other resources. Knowledge of these various sources can strengthen the services provided by librarians who assist forestry researchers through reference services, library instruction, and collection management.