Arising from a joint meeting of the British section of the Society of Protozoologists, The Systematics Association and The Linnean Society which was entitled "Evolutionary Relationships Among Protozoa", this text notes improvements in methods for assessing genetic simliarity. These have led to great changes in scientific understanding of protozoan phylogenetics, and this book aims to bring together the contemporary view on the subject in order to provide a compendium of reference for those interested in the phylogenetics of lower eukaryotes. Opening the symposium, Andre Adoutte surprised many present by suggesting that the 18S rRNA phylogenetic tree of protozoa is probably unreliable. The reasons cited were mutational saturation of sequences and inequalities in evolutionary rates. Further evidence for this theorem was offered in the identification of the deeply incongruent trees that have been obtained using sequences from proteins and the genes which encode them. Some of the data pertinent to this is included in the reviews dealing with relationships among protozoa based on tubulin and on enzymes of central metabolism. It is also suggested in this text that the origins and evolution of organelles such as mitcochondria, plastids and hydrogenosomes are of central importance when considering protozoan phylogenetics. Additionally, the relationships between protozoa, fungi and animals are discussed in two of the reviews, and the authors conclude that animals and fungi each arose by radical transformation of uniflagellate choanozoan-like ancestors.