The hemagglutination assay is a simple and easy method to obtain semi-quantitative data on the sugar binding and specificity of a lectin. An active lectin agglutinates erythrocytes by recognizing a carbohydrate on the cell surface and forming a cross-linked network in suspension. By serially diluting the lectin in a 96-well microtiter plate and adding a constant quantity of erythrocytes, the lectin activity can be estimated.