Add to ORKGThe aim of this thesis is to introduce issues and basic principles of QRS complex detection in ECG signals. This work is separated into several parts. The first part deals with anatomy and functions of the heart, for example the emergence and spread of potentials. The next part includes distribution ECG leads and explanation of ECG signal. Afterwards are described some detectors of QRS complex. The main part of this work is realization of two algorithms implemented in Matlab program. The first detector is based on squaring algorithm and the the second is based on a spreading of the signal into several frequency bands. The effectivness of both detectors is tested on signals from CSE library at the end of the work