The aim of the study was to determine the heart rhythm (the frequency and disturbances) in premature infants in satisfactory clinical condition throughout the 24 hours following birth using Holter method. The influence of some maternal parameters (number of previous pregnancies, delivery mode, usage of pregnancy maintaining drugs) on newborn's heart rhythm and the influence of child's parameters (sex, birthweight, gestational week, clinical state according to Apgar score) were studied. Digital Holter registration system with two channels real-time recording Silicon Beat 2000 version 3.2 by Medea (Poland) was used. Sixty two premature infants were studied. Cardiac arrhythmias were found in 38 cases. They were mainly benign disturbances. The most frequent ones were supraventricular extrasystolic beats. The analysis of the influence of definitive features of mothers and children on arrhythmias and the values of heart rate revealed, that in naturally born infants naturally born and in these ones with low Apgar score the supraventricular extrasystolic beats were significantly more common as compared with those born by Caesarean section and with higher Apgar score. In younger subjects (< 30 gestation weeks) and with lower birthweight (< 2000 g) the sinus tachycardia was significantly more frequent as compared with older and heavier ones.