This volume of Advances in Parasitology has a predominantly protozoological flavor. Key Features * The questionable pathogenicity of Blastocytis, a ptorist closely related to amoeboflagellates * Discussion of Giardia and the evidence of early branching of the eukaryotic stem * Full overview of current knowledge of the immunology of Leishmania * Explanation of the way trypanosomatids transport nutrients and ions across their membranes * A review of the biology of the coccidian parasites of fish with extensive illustrations * A review of the sexuality of parasitic crustaceans