The paper deals with information on the Continuous Glucose Monitoring System (CGMS) and its use in clinical practice. Basic components of the CGMS (sensor, connecting cable, monitor, communication station, computer and software) and directions for the sensor introduction (patient education, check-up of individual components of the CGMS, insertion of the sensor into the subcutaneous tissue, connecting the monitor, sensor initialization and calibration) and monitoring glucose in interstitial fluid (ISF-glucose) are described. The evaluation of optimal accuracy criteria based on clinical research of the CGMS are (1) a correlation between the sensor and meter readings of at least 0.79, and (2) a mean absolute difference of no more than 28 %. Three case-reports demonstrate the authors experience dealing with 1. the results of continuous monitoring of ISF-glucose in a healthy volunteer; 2. development of the dawn phenomenon in a person with type 2 diabetes mellitus documented by an increase of ISF-glucose concentration from 12.5. to 15.1 mmol/l and 3. assessment of the effectiveness of basal rate and prandial insulin doses in a person with type 1 diabetes mellitus treated by means of an insulin pump MiniMed 507.

        Key words: continuous glucose monitoring, selfmonitoring, interstitial fluid, diabetes mellitus, dawn phenomenon.