Anti-HIV (human immunodeficiency virus) active polymethacrylates having pendant sulfated oligosaccharides were synthesized, and the relationship between structures and biological activities of the polymethacrylates was examined. Acetylated 1-Omethacryloyl maltoheptaoside (MA-AcM7) was polymerized with AIBN as an initiator to give polymethacrylates having a pendant acetylated maltoheptaose in every repeating unit, poly(MA-AcM7)s. After hydroxyl groups were recovered by deacetylation, the polymethacrylates having maltoheptaose units, poly(MA-M7)s, were sulfated to give polymethacrylates having sulfated maltoheptaose side-chains, poly(MA-SM7)s, with degrees of sulfation of 1.1 to 2.7 (maximum, 3.0). These polymethacrylates including sulfated oligosaccharides exhibited low anti-HIV activities represented by the 50% protecting concentration (EC 50 ) in the range of 15-62 g/mL and low blood anticoagulant activities around 10 unit/mg (standard dextran sulfate, 22.7 unit/mg). The anti-HIV activity increased with increasing degree of sulfation to reach EC 50 of 15-16 g/mL. In addition, copolymerization of MA-AcM7 with methyl methacrylate (MMA) and subsequent sulfation gave polymethacrylates consisting of various proportions of highly sulfated maltoheptaose and MMA units. It was revealed that the anti-HIV activity increased with decreasing proportion of the sulfated oligosaccharide moiety and that a copolymethacrylate having 22 mol % of sulfated maltoheptaose units (DS Ο 3.0) had a high anti-HIV activity in the EC 50 of 0.3 g/mL. The blood anticoagulant activity increased slightly from 9 to 18 unit/mg with decreasing proportion of the sulfated maltoheptaose units. These results suggested that the biological activities were influenced strongly by the spatial distance between sulfated oligosaccharide substituents in the polymethacrylate main chain. Distinction and conformation of the oligosaccharide side chains also played an important role.