Immunomodulating activities of three carboxymethylated derivatives (AG-AL-CMS, AG-AL-CMI, and AM-APP-CM) of linear (1-->3)-alpha-D-glucans from Agrocybe cylindracea and Amanita muscaria were evaluated with murine peritoneal macrophages playing an important role in tumor immunity. The ratio of macrophages in peritoneal exudate cells increased more than 50% after the administration of three carboxymethylated (1-->3)-alpha-D-glucans. These carboxymethylated (1-->3)-alpha-D-glucans exhibited higher potentiating activities for macrophages than carboxymethylated linear (1-->3)-beta-D-glucan (CMPS) in the potency of reduction of nitro blue tetrazolium, products of nitric oxide and the soluble cytotoxic factor, the amount of glucose consumption, and the activation of acid phosphatase. AG-AL-CMS, AG-AL-CMI, and AM-APP-CM were found to induce the tumor regressing factor in mouse serum, although the ability of the induction of this factor was weaker than that of CMPS. The reticuloendothelial system-potentiating activation of three carboxymethylated alpha-D-glucans was similar to that of the carboxymethylated beta-D-glucan. AG-AL-CMS and AG-AL-CMI, but not AM-APP-CM, were suggested to possess a higher-order structure, resulting from the formation of a fluorescent complex with aniline blue.