Blood concentration of reducing sugar and electrical activity of the duodenum were simultaneously measured in four conscious pigs, each chronically fitted with a catheter in a jugular vein, a duodenal infusion catheter, and transparietal intestinal electrodes. After a meal, blood sugar concentration exhibited cyclic variations at a frequency similar to that of the migrating myoelectric complexes (MMC) observed on the duodenum (1.6 +/- 0.3 per h). During the fasting state (15 h), glucose or xylose infusions into the duodenum also induced blood sugar oscillations at the same frequency as that of duodenal MMC (0.9 +/- 0.3 per h). Injections of xylose boluses into the duodenum induced more rapid and larger increases in blood reducing sugar concentration when injected during the last two-thirds of the phase of irregular spiking activity or during the phase of regular spiking activity than when injected during quiescence or the first third of the phase of irregular spiking activity. It is concluded that intestinal motility is a prerequisite for optimal intestinal absorption of sugar that is markedly enhanced at the time of maximal digesta flow in the pig.