Fructosamine, protein, albumin and HbA1c from 199 diabetics were followed for up to 220 days. An increase in average blood glucose during the preceding 10 days causes an increase in fructosamine by 50 mumol/l. During the day there is little variation in the fructosamine concentration, whereas relating fructosamine to protein or albumin results in substantial fluctuations. A possible cause is the necessity for two measurements which is associated with an increased error. Long term observations reveal a significant correlation between fructosamine and HbA1c which is little affected by relating fructosamine to protein or albumin. Diabetics exhibited significantly lower protein and albumin concentrations than the normal collective, yet the standard deviations from the individual means were only 7 and 7.9%, respectively.