Background and Aim: Pranayama, the art of breath control, is considered to be the heart of yogic exercises. The present study was performed with the aim of evaluating the effect of Pranayama/ Alternate Nostril Breathing (A.N.B.) on the parasympathetic nervous system in healthy young adult males. Methods:A comparative account of the expiratioin: inspiration ratio (E:I ratio) and the orthostatic tolerance test (30:15 ratio) at the basal level, at the start of the study and after the practice of A.N.B for 5 minutes and following a training period of 6 weeks. Result and Conclusion:This study showed that the para sympathetic tone was enhanced appreciably in the participants. The observations of this study suggest that the yogic exercise of A.N.B. influences the parasympathetic nervous system significantly.