The usefulness of the serum fructosamine (Fser) to monitor the retrospective glucose concentrations in transitional dairy cows (n=17) was evaluated. In weekly blood samples (3 weeks before to 5 weeks after calving) concentrations of plasma glucose and serum fructosamine, β-hydroxybutyrate (βOHB) and total proteins were determined. The observed Fser concentrations (271±55 mean value, range 152–423 μmol/l) were within the range reported in the literature, and showed a progressive and significant decrease after calving. Mean plasma glucose concentration was 60·6±5·0 (range 39·9–82·2) mg/dl increasing from week 3 before calving to the week of calving and then decreasing during the next 5 weeks of lactation. This decrease was coincident with inverse relationships between plasma glucose and milk yield (P=0·03) and serum βOHB (P<0·001). Linear regression analysis performed between serum fructosamine and (a) plasma glucose concentration of the same sampling and (b) plasma glucose concentration of 1, 2 and 3 weeks preceding the sampling, did not show significant and systematizing positive correlations. Persistent hypoproteinaemias that could affect the fructosamine concentrations were not found: mean value and range of serum proteins was 6·3±1·0 and 4·8–7·8 g/dl, respectively, and no correlation was found between serum proteins and Fser (P=0·26). Results did not support the possibility of retrospective monitoring of the plasma glucose concentration by serum fructosamine in dairy cows in the transition period.