The aim of this study was to describe the epidemiology of self-monitoring of blood glucose and to identify specific characteristics of those subgroups of diabetic patients treated with insulin that are most likely to monitor their blood glucose according to medical recommendations. Data were collected on 1384 insulin-treated patients, enrolled from 35 diabetic outpatient clinics and 49 general practitioners' offices between December 1993 and June 1994. Seventeen Italian regions out of 20 were included in the study. Our data show that 418 (31%) diabetic patients treated with insulin had never practised blood glucose self-monitoring. In addition, only 242 patients (18.2%) self-monitored their glycemia with a mean frequency of at least once a day (29.7% among insulin-dependent diabetes mellitus (IDDM) and 13.9%, among insulin-treated non-insulin-dependent diabetes mellitus (NIDDM-IT) patients). Patients' characteristics associated with a higher probability of practising blood glucose self-monitoring were age below 50 years, being treated at a diabetic outpatient clinic, hypertension, need of three or more insulin injections per day, history of hypoglycemic episodes, ability to self-manage insulin doses. Our study calls for vigorous efforts aimed at promoting the incorporation of clearly-defined educational programs at each level of care, in order to improve the motivation and self-care of diabetic patients. Furthermore, studies are necessary to identify subgroups of diabetic patients that truly need to self-monitor blood glycemia, and to assess the efficacy of the practice of self-monitoring of blood glucose in improving metabolic control and reducing acute and long-term diabetic complications.