In 127 patients, we investigated the influence of hyperlipemia on observed fructosamine values. An in vitro influence of the lipids on the fructosamine reading could be excluded for cholesterol, HDL-cholesterol and triglycerides. However, in patients with type I diabetes, both, cholesterol and triglycerides significantly (p less than 0.05) correlated with fructosamine. This may be explained by in vivo effects of hyperglycemia on lipids or lipoproteins. For a given level of hyperglycemia, fructosamine is slightly more sensitive than HbA1c.