The aim of the present study was to look for possible associations between the blood glucose variability and twenty-four clinical parameters in ninety-eight patients with Type 1 diabetes mellitus treated with multiple injections of insulin or insulin pumps and practising self-monitoring of blood glucose. The blood glucose variability was measured as the standard deviation of glucose values obtained by self-monitoring at five specified time points every two days for four weeks. The blood glucose variability significantly correlated with the mean blood glucose level (r = 0.48, p = 0.0001) and with the number of hypoglycaemic events (r = 0.31, p = 0.002), but not with HbA1c (r = 0.19, p = 0.07). Significant correlations were also found between glucose variability and patients' variations of insulin dosage (r = 0.31, p = 0.004), duration of diabetes (r = 0.22, p = 0.03), and body-mass index (r = 0.20, p = 0.04). Patients with incipient or clinical nephropathy had more variable blood glucose values, compared with patients without signs of nephropathy (p = 0.03). Other parameters studied, such as other late diabetic complications, the C-peptide level, the insulin dose and the level of insulin-binding to antibodies did not relate significantly to the blood glucose variability.