Resting myocardial blood flow in absolute units was determined in 11 patients without known heart disease using dynamic PET with 82Rb. Based on a modified Fick's approach to measuring myocardial blood flow, originally developed and validated in canine studies by Herrero and coworkers (Circulation 1990; 82: 1377-86), a global flow value of 0.60 +/- 0.10 ml/min/gr myocardium (MV +/- SD, N = 11) was obtained. With the exception of the apex, segmental blood flow was not significantly different in 12 left ventricular myocardial segments, indicating homogenous myocardial blood flow distribution. In 5 patients global myocardial blood flow was determined simultaneously both by 82Rb PET and argon as inert gas method. 82Rb flow did not differ significantly from argon flow (0.60 +/- 0.05 vs. 0.68 +/- 0.15, MV +/- SD, N.S.). These results show that correct quantitation of resting myocardial blood flow with dynamic 82Rb PET is feasible also in patients.