The human immunodeficiency virus (HIV) type 1 envelope protein (recombinant [r] gp160)-induced T cell lymphokine release pattern of chimpanzees immunized with HIVIIIB rpg160 tested and compared with rpg160-induced lymphokine releases of T cells from unimmunized, HIV-1-infected chimpanzees. The results showed that infection of chimpanzees with HIV-1 did not induce rgp160-specific memory T cells (as evidenced by the lack of Th1 and 2 type lymphokine releases after rgp160 stimulation). In contrast, T cells of rgp160-immunized chimpanzees released Th1 type lymphokines upon stimulation with rgp160 of HIVIIIB, HIVMN, and HIVRF. release was comparable whether chimpanzees were immunized with rgp160 only or also challenged with HIV-1 and protected or not protected. Thus, rgp160 immunization leads to generation of Th1 type memory cells. Whether Th1 type responses contribute to protection against HIV-1 infection has yet to be clarified.