Oestrogen has the capacity to suppress T cell‐dependent DTH. To explore the mechanisms whereby oestrogen exerts its effects on the immune system we have used SCID mice which are largely devoid of functional T and B lymphocytes, hence being unable to raise DTH, but display intact antigen‐presenting capacity. Transfer of lymphocytes to SCID mice restores the DTH capacity. In order to analyse if oestrogen down‐regulates DTH by a direct action on T cells we reconstituted SCID mice with either splenocytes or thymocytes from congenic C.B‐17 or allogeneic B6 donor mice. Either donor or recipient mice were exposed to estradiol before cell transfer. DTH response was registered in recipient SCID mice 1 and 3 weeks after challenge with oxazolone (OXA). SCID mice receiving estradiol‐exposed spleen cells from congenic or allogeneic donor mice displayed lower DTH responses compared with control mice. In contrast, SCID mice receiving estradiol‐exposed thymocytes from congenic donor mice showed no significant difference in DTH response compared with control mice. Estradiol‐treated SCID mice, transferred with either spleen cells or thymocytes from congenic, hormonally non‐treated donors, displayed a significantly lower DTH response compared with control mice. In contrast, estradiol‐treated SCID mice receiving hormonally non‐treated allogeneic spleen cells showed no difference in DTH response compared with control mice. The results show that T lymphocytes are not the target cell population for estradiol‐mediated suppression of DTH in reconstituted female SCID mice.