Conagenin (CNG), a low molecular immunomodulator, enhanced incorporation of [3H]thymidine into T cells activated by concanavalin A but did not to non-activated T cells. The culture supernatants of activated T cells treated with CNG enhanced incorporation of [3H]thymidine into cytokine dependent cell lines, CTLL-2 and IC-2 cells. This indicates that CNG exclusively acts on activated T cells and stimulates them to promote DNA synthesis and to produce lymphokines, which may include T cell growth factors and hematopoietic growth factors. These activities were also observed with T cells taken from mice given CNG.