Donald H. Pfister is a professor in organismic and evolutionary biology, curator of the Farlow Library and Herbarium, and dean of the Summer School at Harvard University. His research interests are in plants and in fungi (including lichenized fungi). He and his associates work on elucidating the relationships within a large phylum of fungi, the Ascomycota. They are interested also in the ways in which these fungi are associated with plants—as parasites and mutualists. Their studies use both morphological information and molecular sequence data. Pfister has also published works on the history of botany and has contributed bibliographic work that documents the descriptive literature in plant science. Pfister was honored for 25 years of teaching in the Extension School in 2004 and has received the William H. Weston Award for Teaching from the Mycological Society of America. His undergraduate degree was from Miami University in Oxford, Ohio.