Since 1987 a quality control programme for ward-based blood glucose assays has been established in Lainz Hospital, Vienna. In 1991 following a decision to standardise the type of reflectometer used in the ward, 62 Reflolux IIS reflectance meters (Boehringer Mannheim) were assessed in a quality control consisting of 4 ring trials a year (blood glucose determination in two "unknown" samples) and in daily measurements of control solutions of known glucose concentrations. Experience with this quality control procedure is reported in this presentation of the relevant results of the ring trials. The most frequent errors in performing the test are discussed and the importance of instructing and training the nursing staff in the proper use and maintenance of the meters is pointed out.