BACKGROUND The analytical quality of self-monitoring of blood glucose (SMBG) is not satisfactory, and the need for standardized control routines for SMBG has been underscored. The objective of this study was to investigate whether an external quality assessment scheme (EQAS) designed for office laboratories could improve the quality of SMBG measurements. METHODS From October 2001 through March 2004, we conducted 6 glucose surveys for diabetes patients and coordinated them with an EQAS for office laboratories. Patients received 2 control samples by post twice a year. They measured each control sample in duplicate in accordance with written instructions, returned the results, and received an assessment of their analytical performance. Participants who got a poor evaluation were followed up by phone and were offered guidance. RESULTS Participating in an EQA program over a period of 3 years decreased the percentage of poor results among diabetes patients significantly, from 11.2% to 1.9% in the first and last surveys, respectively. Between-participant CVs improved from 5.5% to 3.7% and were comparable to results from office laboratories. It was difficult to sort out factors contributing to quality improvement. CONCLUSIONS Implementing a traditional EQAS among diabetes patients may improve the analytical quality of SMBG and could be convenient for motivated patients. Further evaluation of the clinical usefulness of implementing such a program is needed, however, and costs as well as limitations of current EQAS for glucose in general should be taken into account.