It is known that acute exercise affects skeletal muscle blood flow (BF) heterogeneity within skeletal muscle, but it has remained to be demonstrated whether increasing exercise intensity and a potent single vasodilator, adenosine, has an effect on muscle BF heterogeneity in humans. In the present study, this was studied by measuring muscle BF and its heterogeneity in m. quadriceps femoris (QF) and within its four different muscle compartments in six healthy non-smoking young women using positron emission tomography. BF was measured first at baseline and then during three incremental work-loads (50, 100 and 150 N) during one-leg intermittent isometric contractions without and with theophylline-induced non- selective adenosine receptor blockade. It was found that mean BF increased and its heterogeneity decreased with increasing work-load both without and with theophylline (p < 0.001). Theophylline did not have effect on muscle mean BF in the whole QF or its four muscle compartments or BF heterogeneity at the level of whole QF. However, it modestly increased local BF heterogeneity within QF muscles (p = 0.03). As a conclusion, this study demonstrates that skeletal muscle BF heterogeneity decreases with increasing exercise intensity, which is due to newly activated muscle mass and decreased mean BF variability between muscles engaged in exercise. Furthermore, blocking of adenosine receptors with theophylline increases local skeletal muscle BF heterogeneity during exercise slightly, but significantly, and do not affect mean bulk BF within the muscle. It seems that adenosine is not an obligatory for causing exercise hyperemia at least during low- and moderate exercise intensities in human skeletal muscle.