In 157 capillary blood samples of type I diabetics parallel determinations of the blood sugar concentration were performed by means of the visual evaluation of the test strips Glucosignal and Haemo-Glucotest 20-800 in comparison to an enzymatic reference method by trained special personnel. On the basis of the correlation coefficients the two test strips showed a good accordance between visual evaluation and the reference method (r = 0.98 and 0.97, respectively). In comparison to the reference method in Glucosignal there is a tendency to underestimation (-0.67 mmol/l), on the other hand in the Haemo-Glucotest 20-800 the blood glucose concentrations are on an average +0.87 mmol/l above the reference value. In visual valuation of the blood glucose concentrations by means of Haemo-Glucotest 20-800 with increasing blood glucose concentration an increasing inexactness is to be stated, whereas Glucosignal is characterized by more favourable parameters of quality.