It was aimed to evaluate the immunological effects of cold and hot aqueous extracts of H. sabdariffa calyces in albino mice. Three oral doses (9.78, 19.56 and 29.34 mg/mouse for cold extract, and 13.72, 27.44 and 41.16 mg/mouse for hot extract) of each extract were evaluated, in addition to the immune suppressive drug etoposide (0.05 mg/mouse/day) and interferon (0.25 mg/mouse/day). Metaphase index, T-rosette formation (bone marrow, thymus, spleen and lymph nodes) and ADA specific activity (serum and thymus) in the investigated organs were significantly decreased in animals treated with etopside as compared with normal controls, while in mice treated with calyx extracts of H. sabdariffa, the investigated parameters were significantly enhanced, especially at the third dose of both extract, and such dose almost shared the effect of interferon in mice treated with it. It was almost universal to observe that hot extract was better than the cold extract. These findings suggests the immune enhancement effects of the investigated extract, and they were in a dose-dependent manner.