αβ and γδ T cells are distinguished by the clonotypic subunits contained within their TCRs. Although the αβTCR has been well characterized, much less is known about the γδTCR. Here, we report that, unlike αβTCRs, most γδTCRs expressed on ex vivo γδ T cells lack CD3δ. Despite this structural difference, signal transduction by the γδTCR is superior to that of the αβTCR, as measured by its ability to induce calcium mobilization, ERK activation, and cellular proliferation. Additionally, the TCR complexes expressed on primary γδ T cells contain only ζζ homodimers; however, following activation and expansion, FcϵR1 γ is expressed and is included in the γδTCR complex. These results reveal fundamental differences in the primary structure and signaling potential of the αβ- and γδTCR complexes.