Plasma fructosamine and glycosylated haemoglobin were measured in insulin-dependent (n = 30) and in non-insulin-dependent diabetics (n = 90) and in healthy controls (n = 45). Fructosamine correlated significantly with glycosylated haemoglobin in the non-insulin dependent (r = 0.5, P less than 0.001) better than in the insulin-dependent group (r = 0.39, P less than 0.05). No correlation was found between plasma fructosamine and albumin or total protein concentrations when the concentrations of albumin and protein are within normal reference range. The fructosamine test has got many desirable characteristics, which will give it a role in the assessment of diabetic control.