The original fructosamine assay, based on reduction of NBT, has been modified and marketed as a kit. The development includes addition of detergents, uricase, change of the buffer and NBT concentrations, and use of a new calibrator. We report the effects of these changes on the measured values of fructosamine in lipemic and uricemic sera. A secondary calibrator produced from pooled serum and stabilized by removal of glucose was used to calibrate the original fructosamine assay and enhance transferability of results. There was no correlation between the difference between the results obtained by the two procedures and the concentration of urate or triglycerides. The development of colour was faster with the original method. It is suggested that measurements of fructosamine by either method are practically equivalent. However, the use of polylysine as a calibrator is advantageous. It is suggested that the generic term S-Glycated proteins is used for the measurand rather than S-Fructosamine which in effect has become a commercial term.