This document presents research on classifying cardiac arrhythmias using frequency domain features extracted from electrocardiogram (ECG) signals. Features are extracted from ECG data using Discrete Cosine Transform to calculate the distance between RR waves. These frequency domain features are then classified using various machine learning algorithms, including Classification and Regression Trees, Radial Basis Function networks, Support Vector Machines, and Multilayer Perceptron Neural Networks. Experiments were conducted on the MIT-BIH arrhythmia database to evaluate the performance of the different classifiers.