A fast, sensitive, interference-free, single enzyme single reagent glucose biosensor, operated in flow injection analysis (FIA) mode, was developed. The method used involved formation of colored complex of titanium sulfate reagent with the peroxide generated by glucose oxidase immobilized in a packed bed reactor. The color developed was detected spectrophotometrically in a flow cuvette. The system could measure down to 0.5 mg glucose l(-1) and the response was reproducible and linear in the range 1 mg l(-1) to 100 mg l(-1). The analysis time for a 500 mu l sample was 35 s and was free of interference from a number of substances tested. Analysis results using an off-line batch kit were observed to be in agreement with the developed system for determination of glucose in blood plasma samples.