Recently, Medisense has introduced the Sensorlink system as a tool for retrieving the 125 last results of home blood glucose monitoring stored in patient's Pen 2 or Companion 2, unknown to them. Therefore we decided to check the compliance of type I diabetic adolescents and young adults with home blood glucose monitoring (HBGM) by comparing the blood glucose values noted in their log book and those retrieved by the Sensorlink and to evaluate an eventual subsequent effect both on compliance and glycated haemoglobin (HbA1c). The study was carried out in 60 insulin-dependent diabetes mellitus (IDDM) patients (33 women and 27 men) chosen according to two criteria: (1) the use of a Medisense Pen 2 or Companion 2; (2) autonomous self-monitoring of blood glucose, i.e. without parental supervision. They were aged 21.3 +/- 6.3 years with a diabetes duration of 11.6 +/- 7.0 years. HbA1c was measured by an HPLC method (N: 4.4-6.0%) before and after the first use of the Sensorlink and HBGM data of the log books were recorded. After the first use of the Sensorlink, the patients were warned of the retrieving data. The 60 patients were divided into two groups (same mean age and diabetes duration), according to the mean level of HbA1c before Sensorlink: < or = 7% (good control; n = 33); > 7% (insufficient control; n = 27). Cheating was unrelated to sex and occurred in 36 patients (60%; aged: 19.3 +/- 4.7 years), up to 100% in 13 of them (22%); five patients had no log book (8%; aged: 24.0 +/- 5.0 years); 19 patients (32%; aged 24.4 +/- 7.9 years) didn't cheat at all. After the use of the Sensorlink system, cheating dramatically decreased to zero. The effect of the Sensorlink system on improvement of HbA1c was statistically significant in the 27 patients with insufficient control before Sensorlink, since mean HbA1c level decreased from 8.0 +/- 0.9% to 7.5 +/- 1.1% (P < 0.05). In conclusion, non compliance with HBGM occurs in 2/3 of adolescents and young adults with IDDM. The Sensorlink system puts an end to this phenomenon and allows significant reduction of HbA1c levels in patients with insufficient metabolic control.