Unit for Holter-cardiography in Mostar Clinical Hospital started in 1987. With one holter cassete we examined employees in SOKO factory in Mostar. Unfortunately, recorded cassetes had to be read in Belgrade because we had no competend reader. In 1999 we got a new Holter with 3 cassetes and computer software. That was how we improved diagnostic of rhythm disturbances and ST changes in our Unit. In year 2000. we examined total of 84 patients: age 14 to 40 years 14 (16.7%), age 40-60 33 (39.3%), 60 years and up 37 (44%). There was 53 (63.10%) of male and 31 (36.90%) of female patients. We stress importance of nurse in prepareing of patient for holter monitoring, especially in electrode placement, teaching patient about diary sholud be followed during 24 hours of monitoring, protect equipment from damage and to notice possible disturbances. Important is a role of sthe nurse in patients data storage. For this reasons, an additional education is needed for nurses employed in Unit for Holter-cardiography.