OL-2, a highly branched (1→3)-β-D-glucan, is an antitumor glucan showing strong hematopoietic activity with weaker adjuvant activity than schizophyllan (SPG), also an antitumor glucan and one which is clinically used. This paper deals with the gene expression of the interleukin 1 (IL-1) family in mice by OL-2 and SPG in order to characterize the immunopharmacological activity. Gene expression was examined by reverse transcriptase-polymerase chain reaction method. Intraperitoneal administration of OL-2 (250 μg/mouse) expressed all three genes of IL-1α, β, and IL-1 receptor antagonist (IL-1ra) in the peritoneal exudate cells, while SPG induced a strength of IL-1α mRNA comparable to that by OL-2 but a weaker level of IL-1β mRNA. SPG did not induce IL-1ra. Similar patterns were seen in spleen and liver by OL-2 or SPG administration. These findings suggest that the immunopharmacological characteristics of (1→3)-β-D-glucan are regulated under the gene expression of the IL-1 family.