We report an abnormal pattern for enolase (EC 4.2.1.11) isoenzymes in the serum of a patient with squamous cell lung carcinoma. The alpha alpha-isoenzyme was present but the alpha gamma form was not detected, and near the point of application on the electrophoretogram was an abnormal band. We determined that the abnormal fraction corresponded to a macroenolase, composed of the alpha gamma-isoenzyme complexed with IgG. From a practical point of view, the presence of such a macroenolase, containing gamma-subunits, results in falsely increased results for neuron-specific enolase (NSE) in procedures that determine only the NSE concentration without consideration of the enolase isoenzymes.