1-11C-n-Butanol produced semiautomatically using a cyclotron was employed to investigate the whole-body distribution and kinetics of the label of this compound. Following the administration of 11C-butanol into the aorta of two dogs, more than 80% of the activity was cleared from the blood within 1 min. The activity distribution mirrored the cardiac output distribution as determined using 121I microspheres. Within 25 min p.i., a significant release of decay-corrected activity was only observed for the liver, spleen, and kidneys. Muscle and whole-body activity showed constant levels during this period. In 45 tumor transplants from rats, the dynamic behavior of the label was studied. The tissue retention of activity following injection into the a. femoralis was approximately 100% during the 1st 15 s for both tumor and muscle (n = 6). The activity release by tumors during the 1st 10 min after intra-aortic injection was 18% +/- 4.5% (n = 39; decay corrected). In five different tumor lines (n = 10), the initial 11C-butanol uptake was related to that of muscle, and the results were correlated with the tumor-to-muscle retention of 121I-microspheres (r = 0.89). In 17 tumors, the correlation between 11C-butanol uptake and the washout rate of 133Xe resulted in a correlation coefficient of 0.96. Tumor-to-muscle uptake ratios could be equally determined using intra-aortic and intravenous injection, as evaluated by intraindividual comparison in 12 rats (y = 0.01 + 0.98x; r = 0.98). 11C-Butanol appears to be an appropriate radiotracer for the assessment of blood supply to malignant tumors relative to muscle.