Alloreactive T cell clones with distinct specificities were used to raise anti-idiotypic antisera via an F1 anti-(parent anti-F1) protocol. Antisera were raised that could stimulate the proliferation of the appropriate T cell clone, but not other clones. The active fraction of the antisera for T cell proliferation was immunoglobulin. In addition to proliferation, an anti-idiotypic antiserum could induce the appropriate T cell clone to secrete substantial amounts of interleukin 2 (IL-2). Production of IL-2 appeared independent of the involvement of accessory cells. These accessory cells may be unnecessary for IL-2 production in our assay, or their effect may be produced by anti-idiotype. Thus, anti-idiotype may provide two or more specific T cell signals.