This work presents a methodology for detection of QRS complexes which is an adaptation of Pan-Tompkins algorithm. This method includes band bass filtration, derivative, squaring, moving window integration, thresholding, false peak cancellation and detection the predominant peak of QRS complex. This method doing well in the presence of noise and simple ectopic beats but still affected by multifocal ectopic beats. The method was tested on the MIT-BIH Arrhythmia database and achieves accuracy 99.68%.