With increasing frequency, systematic and evolutionary biologists have turned to the techniques of molecular biology to complement their traditional morphological and anatomical approaches to questions of historical relationship and descent among groups of animals and plants. In particular, the comparative analysis of DNA sequences is becoming a common and important focus of research attention today. This volume surveys the emerging field of molecular systematics of DNA sequences by focusing on the following topics: DNA sequence data acquisition; phylogenetic inference; congruence and consensus problems; limitations of molecular data; and integration of molecular and morphological data sets. The volume takes its inspiration from a major symposium sponsored by the American Society of Zoologists and the Society of Systematic Zoology in December, 1989.