Abstract: A method is described for the rapid, sensitive and accurate determination of sucrose in biological fluids. A substrate is pre-coated with a glucose or fructose polymer and a transglycosidase enzyme. When the coated substrate is incubated with biological fluids containing concentrations of sucrose, the transglycosidase enzyme transfers monomers of glucose or fructose from the sucrose to the glucose or fructose polymer. The dimensions of the polymer are increased in proportion to the sucrose concentration of the samples. Newly formed polymer is subsequently quantitated in an immunoassay which employs either a combination of a carbohydrate-binding protein (which may be an antibody) and a conjugate of a secondary antibody and a marker enzyme, or a conjugate of a carbohydrate-binding protein and a marker enzyme. The assay is accurate at sucrose concentrations below 1 .mu.g/mL. No interference was observed at glucose concentrations as high as 25 mM.