Complete annotation of the predicted Toxoplasma gondii proteome provides a first estimate of the repertoire of extracellular (EC) proteins involved in a landscape of host–parasite interactions. During the evolutionary process of specialization that led to parasites of the genus Toxoplasma, the most rapidly evolving events involved the acquisition or streamlining of metabolic pathways and, the subject of this chapter, the invention of new proteins that function at the parasite membrane surface. The extensive repertoires of parasite membrane surface and secreted proteins can be viewed as incubators harboring diversity and mutability that facilitate genetic selection and evolution. This chapter describes the catalog of predicted EC proteins encoded within the Toxoplasma gondii genome sequence proteins that likely regulate a variety of cellular processes and host-parasite interactions, such as maintenance of cellular and surface membrane structures; recognition and response to host tissues and cell surfaces; host tissue and cell invasion; and evasion and manipulation of host-immune responses. The chapter also serves as a reference companion to Toxoplasma invasion of host cells and the post-translational proteolytic modifications of surface proteins.