The water-ethanol extracts of the cultured mycelia of 17 species of Cordyceps and six species of Isnria were each examined for the presence of Ca'+ antagonists and inotropic agents using the left atrium of the guinea pig in vitro system. The extracts from two of the Cordyceps species and four of the Isaria species showed strong activity in both tests. The active compound was isolated from the extracts and identified as N 6-(2-hydroxyethyl)adenosine. This is the first time that synthetically known compound has been isolated from biological sources. At the same time, the extracts of these CordyLeps and Isaria species were examined for the presence of cordycepin and adenosine.