1) Oral administrated Adenosine was rapidly absorbed from gastrointestine. However, there was no significant incorporation into the tissues (organs) such as heart. 2) Intravenously administrated Adenosine was significantly incorporated into the tissues (organs) such as heart. And the incorporation into the nucleotide-fractions (AMP, ADP and ATP) was high and that into the nucleoside-fractions was low. Particularly, it was interested that the incorporation-ratio into the myocardial ATP + ADP fraction was higher than those of other tissues (organs). 3) The most part of Adenosine was incorpo-rated into the myocardial ATP fraction in the perfusion of isolated rat heart. 4) However, the most part of Adenosine was incorporated into the nucleoside-fractions in the slice-experiment. 5) It was thought that the most part of oral and intravenously administrated Adenosine was excreted in the urine.