Combinatorial libraries of peptide dendrimers bearing two and four copies of C-fucosyl residues were screened for binding to fucose specific lectins leading to potent ligands for Ulex europaeus lectin UEA-I (IC(50) = 11 microM). The dendrimers also show high affinity for the lectin PA-IIL (IC(50) = 0.14 microM) from the pathogenic bacteria Pseudomonas aeruginosa. The dendrimers described are the first multivalent ligands for these lectins. In our system, glycopeptide dendrimer-protein binding is modulated by the nature of the amino acid residues present in the dendritic structure instead of depending solely on the number of sugars attached to the scaffold. Studies of colchicine-glycopeptide dendrimer conjugates with improved selectivity for cancer cells in comparison to colchicine are also described.