There has been considerable interest in the serum fructosamine assay as a measure of glycated serum proteins. We have measured serum fructosamine in three groups of patients--those with uraemia; those with multiple myeloma; and those with acute inflammatory conditions--none of whom were known to have diabetes. Serum fructosamine was significantly higher in the uraemic group than in the other two, and also than in a control group. When allowance was made for prevailing serum albumin levels fructosamine was shown to be increased in the acute inflammatory group also. There was a significant correlation between random plasma glucose and serum fructosamine only when fructosamine was adjusted for prevailing albumin levels. In control and uraemic subjects there was a significant positive correlation between serum fructosamine and albumin levels, whereas in the myeloma group there was a negative correlation with serum protein. These data would suggest the need to take into account serum albumin levels and protein composition if serum fructosamine is accurately to reflect short-term integrated glycaemia.