After removal of the labile material, we have measured the stable glycosylated fraction of haemoglobin with a new, commercially available, phenylboronic acid affinity gel, Glycogel B. The mean value was established for 61 non-diabetics as 7.31 (SD +/- 0.92)% and for 108 diabetics as 12.70 (SD +/- 2.88)%. The method is highly reproducible with a coefficient of variation below 2.0%. The effect of changing the temperature from 7 degrees C to 37 degrees C, and pH from 8.1 to 8.9 was investigated. For accurate results the temperature should be maintained between 20 degrees C +/- 1 degree C, and the pH between 8.6 +/- 0.1. A poor, but significant correlation (r = 0.43) between glycosylated haemoglobin and simultaneous blood glucose was shown. There was a good correlation with the agar gel electrophoretic method (r = 0.95). The slope of the regression line was 1.20 which indicates that this affinity method measures more than just HbA1. The affinity method appears to offer selectivity for diabetics than the electrophoretic method.