Although the patterns of lymphokine (LK) secretion by CD4 and CD8 alpha beta T cells have been extensively studied, the question of whether gamma delta T cells display patterns of restricted LK production and whether these patterns are the same as seen in conventional alpha beta T cells has not been previously addressed. In this study we generated panels of gamma delta T cell clones from normal C57BL/6 and BALB/c mice using a lectin-driven system and compared their patterns of secretion of nine LK with those of CD4 and CD8 alpha beta T cell clones generated in the same system. The results showed that gamma delta T cell clones displayed nonrandom patterns of highly restricted LK production with a strong bias towards the production of type 1 LK. The dominant pattern was one of high level secretion of interferon-gamma and tumor necrosis factor (TNF), with variable production of interleukin (IL)-2, and little or none of the type 2 LK IL-4, IL-5, IL-6, and IL-10. This pattern differed significantly from that of CD4 Th1 clones in that gamma delta clones showed a striking deficiency in the production of IL-3 and granulocyte/macrophage colony-stimulating factor. A small subset of gamma delta clones displayed a novel pattern, in which the only LK produced in substantial quantity were TNF and variable amounts of IL-2. The bias of gamma delta T cells towards type 1 LK production was not an artefact associated with cloning because bulk populations of splenic gamma delta T cells behaved in the same way, even when activated in the presence of high concentrations of IL-4.