Typically involving a high number of binding sites and determined by a specific sugar code, lectin binding is usually rapid and strong. Lectins have been focused upon for more than 20 years and are becoming excellent candidates for drug delivery and targeting. Some of problems are associated with lectins because of their large molecular weights. Molecular weights of most lectins are more than 10 KDa that likely results in toxicity and immunogenicty. These problems are probably overcome by small size lectins with high target specificity. As far as we know, two small size lectins have been found. They are Clindamycin Selenocosmia huwena lectin-I and h-defensin. Selenocosmia huwena lectin-I is identified from the venom of the Chinese bird spider Selenocosmia huwena. It is composed of 32 residues including three disulfide bridges with homology with N-terminal fragment of great nettle lectin. h-defensin is purified from the leukocytes and bone marrow of the rhesus macaque. h-defensin is an antimicrobial peptide with capability to protect cells from in vitro infection by HIV-1. h-defensin is circular, tetracyclic peptides with three disulfide bridges connecting its antiparallel b-sheets and composed of 18 residues. It can specially bind to galactosylceramide. Although they have a small size, it is not easy to manipulate and develop Selenocosmia huwena lectin-I and h-defensin as drug targeting systems because of their complex circular structures and multiple disulfide bridges. The structural organization of the precursor is quite similar to amphibian antimicrobial peptide precursors, comprising a signal peptide sequence, an N-terminal spacer peptide region containing several aspartic and glutamic acid residues, and the mature peptide at the C-terminus of the precursor. The amino acid sequences deduced from the cDNA sequences match well with the amino acid sequences determined by Edman degradation. Since the precursor of odorranalectin shares a similar signal and propiece peptide with the previously identified amphibian antimicrobial peptides, we suspected that it had antimicrobial activities. In contrast to our speculation, odorranalectin had no antimicrobial activities. Odorranalectin could strongly agglutinate intact, trypsin-, or formaldehyde-treated rabbit erythrocytes, however more odorranalectin was needed for agglutinating proteinase-treated rabbit erythrocytes. The minimum concentration to agglutinate intact human erythrocytes is 0.75 mg/ml. EDTA Estradiol Benzoate treatment and metal cation addition to odorranalectin did not affect the agglutinating activity, which suggested that odorranalectin did not depend on metal cation to exert its lectin-like activity.