Adenosine, the endogenous purine, through its action on four adenosine receptors, is involved in various processes in the heart, such as regulation of the oxygen demand, decrease in sympathetic tone, cell pre-conditioning, inflammation and angiogenesis. Four adenosine receptor subtypes mediate these effects: A1, A2A, A2B, and A3. These make adenosine and its receptor modulators a great candidate for reduction of morbidity and mortality in various cardiac diseases.