Ten dissimilar electrocardiographic (ECG) patterns associated with right bundle branch block (RBBB) are presented. Electrophysiologic basis of the changes is discussed and possible causes for such diversity outlined. We have not found any aetiological association to this variation. The morphological diversity in RBBB patterns is likely to be related to multiple factors--site of block, nature of defect (functional, necrosis, fibrosis), degree of conduction delay, and associated pathologies with their own ECG patterns. Distinguishing RBBB from a normal ECG-variant like rsr' is particularly important when associated with left hemiblocks as the latter situation warrants extensive cardiac evaluation.