Recovery of myocardial adenosine triphosphate (ATP) following moderate periods of ischemia is dependent upon the availability of adenosine monophosphate (AMP) and diphosphate (ADP) for rephosphorylation. Recovery of AMP and ADP levels following ischemia is, in turn, determined by the rates of salvage and de novo adenine nucleotide synthesis. Phosphoribosyl pyrophosphate (PRPP) availability is rate limiting in both salvage and de novo nucleotide synthesis. Parenteral ribose infusions in rats have been documented to elevate myocardial PRPP levels with resultant enhancement of adenine nucleotide synthesis. In this study postischemic recovery of myocardial function and ATP levels in isolated, working rat hearts given ribose infusions before and after ischemia was compared with recovery in control hearts subjected to the same protocol without ribose administration. The mean percent of functional recovery in control hearts following 15 minutes of warm ischemia reached values of 56.7% ± 4.1%, 63.5% ± 4.3%, 65.9% ± 4.6%, and 70.5% ± 4.7% at 2, 5, 10, and 15 minutes of work following ischemia. Hearts perfused with ribose demonstrated improved mean percent return of function at similar intervals of postischemic work with values of 67.9% ± 4.2%, 73.7% ± 3.7%, 81.0% ± 3.5%, and 85.4% ± 3.3%, respectively. Determinations of myocardial ATP levels (μmoles/gm of dry weight) made at the end of 15 minutes of postischemic work were significantly higher (p < 0.02) in the ribose-treated hearts (18.9 ± 0.7) than in controls (16.3 ± 0.6). Infusion of ribose before and after ischemia is a biochemically logical method of improving postischemic myocardial ATP and functional recovery by manipulation of adenine nucleotide synthetic pathways.