In the myocardial interstitial space, adenosine and its metabolites are important markers of ischemia, regulators of blood flow, and may produce cardioprotection against ischemia. A fast and sensitive method to assess the concentrations of adenosine and its metabolites is necessary to determine their involvement in mediating these effects. A method for the simultaneous determination of adenosine, inosine, hypoxanthine, xanthine, and uric acid in the interstitial fluid of the canine myocardium was developed using microdialysis, microbore column high-performance liquid chromatography, and a photo diode array detector (DAD). The microdialysis samples were injected directly onto a microbore C₁₈reverse-phase column without any prior sample preparation. Use of a DAD in this method provided many advantages. First, a DAD allowed the simultaneous detection of UV absorbance at multiple wavelengths, allowing the detection of each compound at their maximal UV absorbance. Further, the full UV absorption spectrum was recorded for each detected peak, confirming peak purity and identity. Using a microbore HPLC column and detection of UV absorbance at the maximal absorbance for each compound improve the sensitivity for all compounds. The detection limit of these compounds is 50 fmol (signal-to-noise ratio, S/N = 3). This method is useful in analyzing the temporal effect of a prolonged period of myocardial ischemia and reperfusion upon interstitial adenosine, inosine, hypoxanthine, xanthine, and uric acid concentrations in anin vivocanine model.