BACKGROUND: Acupuncture treatment on injured cerebral axons has shown to provide efficacy in clinical practice. It is unknown whether acupuncture produces therapeutic effects by protecting injured cerebral myelin in ischemic stroke. OBJECTIVE: To test whether acupuncture provides protection for injured cerebral myelin, based on quantitative data from cerebral ischemia-reperfusion rats, and to compare the effects of early and late acupuncture on serum myelin basic protein (MBP) content and remyelination of the ischemic internal capsule. DESIGN, TIME AND SETTING: A randomized, controlled experiment was performed at the Neurobiological Laboratory, Sichuan University from March 2005 to March 2006. MATERIALS: "Hua Tuo" Brand filiform needles were produced by the Medical Instrument Factory of Suzhou, China. METHODS: A total of 52 adult, healthy, male, Sprague Dawley rats were randomly assigned to four groups: control (n = 4), model (n = 16), early acupuncture (n = 16), and late acupuncture (n = 16). The focal cerebral ischemia-reperfusion model was established by middle cerebral artery occlusion in the right hemisphere using the modified thread embolism method in the latter three groups. Early and late acupuncture groups underwent acupuncture after ischemia for 30 minutes and 2 hours using the Xingnaokaiqiao needling method, respectively. Acupoints were "Neiguan" (PC 6) and "Sanyinjiac" (SP 6) on the bilateral sides, as well as "Shuigou" (DU 26) and "Baihul" (DU 20) with stimulation for 1 minute at each acupoint. Acupuncture at all acupoints was performed two or three times while the needle was retained, once per day. No special handling was administered to the control group. MAIN OUTCOME MEASURES: For each group, remyelination of the internal capsule was observed by Pal-Weigert's myelin staining and serum MBP content was detected using enzyme-linked immunosorbent assay method on days 1, 3,5, and 7 following ischemia-reperfusion injury. RESULTS: Compared with the control group, massive demyelination of the internal capsule occurred, and serum MBP content increased in the model group (P < 0.05). Compared with the model group, the extent of demyelination in the internal capsule was less distinct and serum MBP content was significantly less in the early and late acupuncture group (P< 0.01). Compared with the late acupuncture group, serum MBP content reached a peak later and the peak value was less in the early acupuncture group. CONCLUSION: Results suggest that acupuncture exerts a protective effect on injured cerebral myelin in ischemia-reperfusion rats by reducing serum MBP content and promoting remyelination. The study also suggests that the effect of early acupuncture is superior to late acupuncture.