In order to obtain some insight into understanding of the multivalent interactions between polysaccharide fragments as ligands and lectins conjugated on the membrane surface of lipid vesicles as receptors, two kinds of lectin-conjugated lipid vesicles were prepared, and studies on agglutination and binding were performed with two kinds of microscale assays by applying these to two model systems consisting of different ligands and receptors. The agglutination studies based on the interaction between plant galactomannan fragments and Ricinus communis agglutinin-conjugated lipid vesicles indicated three possible cases of interaction; strong agglutination was caused by large-size fragments with high side chain density, moderate agglutination by medium-size fragments with low side chain density and no agglutination by small-size fragments. The binding studies based on the interaction between yeast mannan fragments and concanavalin A lectin-conjugated lipid vesicles, together with glycosyl-linkage composition analyses, suggested that binding efficiency should be correlated with the structural characteristics of ligands such as size of fragments, rate of branching, and number of high-affinity residues.