We searched for nutrient deficiencies that could cause cardiac arrhythmias [premature atrial contractions (PACs), premature ventricular contractions (PVCs), atrial fibrillation, and related sinus pauses], and found literature support for deficiencies of taurine and l-arginine. Case histories of people with very frequent arrhythmias are presented showing 10-20g taurine per day reduced PACs by 50% and prevented all PVCs but did not prevent pauses. Adding 4-6g of l-arginine immediately terminated essentially all remaining pauses and PACs, maintaining normal cardiac rhythm with continued treatment. Effects of taurine useful in preventing arrhythmias include regulating potassium, calcium and sodium levels in the blood and tissues, regulating excitability of the myocardium, and protecting against free radicals damage. Taurine restored energy and endurance in one of the cases from a debilitated status to normal. Arrhythmias may also respond to taurine because it dampens activity of the sympathetic nervous system and dampens epinephrine release. l-arginine may have anti-arrhythmic properties resulting from its role as a nitric oxide (NO) precursor and from its ability to restore sinus rhythm spontaneously. Endogenous production of taurine and l-arginine may decline in aging perturbing cardiac rhythm, and these "conditional" essential nutrients therefore become "essential" and require supplementation to prevent morbidity and mortality. l-arginine is hypothesized to prevent cardiac arrhythmias by NO stabilization of the sinus node. Cardiac arrhythmias having no known cause in otherwise healthy people are hypothesized to be symptoms of deficiencies of taurine and arginine.