The effect of acupuncture stimulation at Zusanli point (ST.36) on the bioavailability of radio-pharmaceutical 99mTc-sodium pertechnetate (Na99mTcO4) in Wistar rats was investigated. Ten healthy rats were allocated into two groups of five. Group 1 (n=5) was treated by acupuncture by inserting stainless steel needles bilaterally at ST.36; Group 2 was the untreated control. Ocular plexus administration of 0.3ml of Na99mTcO4 (3.7MBq) was carried out 10 minutes after every needle insertion. The rats were killed 25 minutes later. The organs were isolated, the radioactivity determined in a well gamma counter, and the percentage of injected radio-pharmaceutical dose per gram of tissue (%ID/g) was assessed for each organ. The %ID/g varied significantly (p<0.05) between Group 1 and Group 2 in pancreas (0.91 +/- 0.17 vs 0.15 +/- 0.03), stomach (7.97 +/- 0.68 vs 3.51 +/- 0.22), spleen (0.97 +/- 0.11 vs 0.41 +/- 0.14), brain (0.19 +/- 0.09 vs 0.09 +/- 0.04), kidneys (0.91 +/- 0.17 vs 0.15 +/- 0.03), heart (0.81 +/- 0.17 vs 0.31 +/- 0.02) and testis (0.46 +/- 0.04 vs 0.14 +/- 0.03). These findings suggest that the effect of acupuncture at ST.36 modulated organs and tissues responses in rats. Using Chinese theories of Zang-Fu and Five Phases, we suggest that the relationship between acupoints and organs may be related to neuromodulation mechanisms such as somatovisceral reflex responses, which play an important role in the autonomic nervous system. These results also suggest that the effect of acupuncture on the bio-availability of radio-pharmaceuticals may help our understanding of the action of acupuncture points on various organs and tissues.