The ability of the Boehringer Mannheim Reflocheck® glucose monitor to measure blood glucose concentration precisely and accurately over the whole of the clinically relevant range was examined. Data obtained in the plasma glucose range (4–10 mmol/l) confirm the previously reported good performance of the instrument. However, in the low normal and hypoglycaemic range it consistently overestimated plasma glucose levels by a variable amount, making it unsuitable, except as a screening instrument, for the investigation of spontaneous hypoglycaemia. Analysis of paired estimations on the same blood sample showed that the readings obtained were reproducible and not therefore due to sampling error.