The presence in Plasmodium falciparum of a mitogenic factor for the major human blood gammadelta T-cell subset has been known for years. These gammadelta T cells bearing T-cell receptor Vgamma9 and Vdelta2 variable regions also respond to Mycobacterium tuberculosis, through recognition of several phosphorylated nonpeptidic antigens. In this study, we undertook a better characterization of the malarial stimulus and show that the polygonal activation of Vgamma9/Vdelta2 gammadelta T cells by P. falciparum schizonts is also and exclusively attributable to two phosphorylated malarial compounds. The finding of such stimuli in eukaryotic cells evidence an antigenic link between intracellular parasites as different as Plasmodium and Mycobacterium species. Hence, phosphorylated antigens could be involved in a common pattern of transdisease T-cell responses against various human pathogens.