An enzyme thermistor assay for serum glucose is described. The glucose present in the sample is reacted in a small column containing glucose oxidase immobilized to controlled pore glass (single thermistor device). The heat produced in the primary reaction is measured directly in the column without any need for coupling reactions. The useful linear range is 0.01-0.45 mM glucose, permitting 50-fold dilution of serum samples. Advantages are low enzyme cost, due to the immobilization, insensitivity for the color or any turbidity of the sample, and no requirement for coenzyme or any ancillary reaction. Improved sensitivity and extended linear range (0.01--0.9 mM) can be attained through a secondary reaction using catalase. The application to glucose analysis of a split-flow enzyme thermistor equipped with a reference column to eliminate unspecific heat effects is also described. The enzyme thermistor determinations were also compared with a spectrophotometric continuous flow technique using a small column with immobilized glucose oxidase and 4-aminoantipyrine and phenol as color reagents.