Objective. Dopamine interacts with metabotropic receptors. The receptors "move" metabolism but it is not known in which direction or to what degree. We recently showed that dopaminergic neurotransmission varies with the sensation- seeking propensity of healthy volunteers, as assessed by the Zuckerman sensation-seeking scale (ZSSS) scores (1994). We concluded that higher ZSSS scores are associated with higher dopamine concentrations and receptor numbers, and we claim that these differences could be reflected in brain energy metabolism (CMRO2) differences. Methods. To test the hypothesis, we compared the ZSSS scores with CMRO2 measures in 10 men and 9 women aged 19-59 years who twice underwent ECAT EXACT HR 47 whole-body tomography with inhalation of [15O]O2 (1000 MBq). The subjects engaged a digitized version of the Iowa Gambling Task (IGT) in a baseline condition followed by activation. We used anatomical MRI of to co- register brains to PET images. We used the FMRISTAT analysis to test for the existence of brain regions in which CMRO2 values and ZSSS scores maintained a significant correlation. Results. The FMRISTAT analysis identified a significant negative correlation between the ZSSS scores and CMRO2 in several brain regions, including the caudate nucleus and putamen, and the occipital and part of the frontal cortices: This correlation existed only in the healthy men and only when they engaged the IGT. The correlation arose because the healthy men with lower ZSSS scores raise CMRO2 when they engage the IGT, while men with higher ZSSS scores lower CMRO2 when they engage the IGT. There were no positive or negative correlations when women engaged the IGT. Conclusion. The results explain the puzzling two- fold variability of CMRO2 among healthy people recently identified in our study of 49 normal humans (see abstract of Aanerud et al.).