The traditional perception of atrial fibrillation (AF) as having random and disorganized electrical activity has begun to fade over recent years. Studies involving intra cardiac mapping have shown evidence of an underlying spatial and temporal organization in the atria during AF. In this study, we used a modified QRS-T cancellation method for multi-lead ECGs and examined vectorcardiograms synthesized from twenty 12-lead ECGs recorded during AF. As a preliminary study we also analyzed ECG recordings taken during an ablation procedure of a typical atrial flutter patient where mechanisms and activation sequences were well known. Of the twenty synthesized vectorcardiograms of AF, five showed a consistent cyclical vector sequence. The other recordings often showed segments of repeated sequences lasting two or three f-wave cycles.