During our search for macrophage stimulating compounds from medicinal plants, we isolated biopolymers from Acanthopanax sessiliflorus. Isolated fraction AS-5 showed maximum potential, and stimulated lysosonal enzymatic activity by 230% at $300;{mu}g/ml$. The nitric oxide (NO) producing ability of AS-5 $100;{mu}g/ml$ was $58;{mu}M$ when treated with interferon-$gamma$ and lipopolysaccharide $20;{mu}g/ml$. The lymphocyte proliferating effects of isolated biopolymer fractions were also investigated. Highest lymphoproliferative activity (a 2.8-fold enhancement compared to saline treated group was exhibited by AS-3 at $200;{mu}g/ml$ followed by AS-5 and AS-6. The AS-3 fraction stimulated only T-lymphocytes and had little or no effect on B-lymphocyte proliferation. Partially methylated alditol acetates were prepared to elucidate the glycosyl linkage-compositions of the AS-3 and AS-5 biopolymers, and were analyzed by GC-MS. The AS-3 and AS-5 biopolymer fractions were found to contain 2,3,4-tri-O-methyl-D-glucitol, 2,3,4-tri-O-methyl-D-galacitol 3,4,6-tri-O-methyl-galacitol, 2-O-methyl-arabinitol and 2,4,6-tri-O-methyl-D-glucitol, 2,3,6-tri-O-methyl-D-galacitol linkages, respectively.