AIM To observe the features of acupuncture and meridians by measuring transcutaneous CO2 emission(TCE).METHODS A high sensitive CO2 analyzer was used to measure the TCE. TCE on 31 levels of meridianpoints and control points along stomach meridian on leg, large intestine meridian on arm (30) andpericardium meridian on whole course (22) were measured. During needling Jianshi (P5), the changes ofTCE on distal side, proximal side and outside of the pericardium meridian were measured in 20 healthypeople. TCE on 24 source points of twelve meridians in 30 healthy people and some related source points inpatients were measured. TCE on source points, connecting points and sea points in 20 healthy cases weremeasured. Acupoints and reference points (no opening time) were measured on the opening time and nonopening time according to day-prescription in midnight-noon Ebb-flow law in 15 healthy people. The relationbetween TCE and skin temperature and TCE change after muscular exercise were also studied.RESULTS The mean TCE on the meridians was significantly higher (P<0.05, same below) than controlpoints. About 40% levers showed significantly higher TCE on meridian points than on control points amongwhich two third were acupoints, mostly were Jing point and He point where Oi were rich. TCE increasedsignificantly in both the meridian and control points during the needling, while moderately increased on themeridian line, particularly the proximal direction. The correlative coefficient (CC) between the points alongpericardium meridian was 0.65 between acupoi, nts which was significantly higher than 0.56 between nonacupoints. For the 24 source points, CC between the points on same meridian, exterior meridian and internalmeridian, same named hand and foot meridian and normal meridian were 0.81, 0.65, 0.51 and 0.38respectively with significant difference. The mean CC between connecting points was 0.67, significantlyhigher than 0.61 between source points and 0.56 between sea points. The imbalance degree (ID) betweenleft and right meridian points, Yin and Yang meridian points and same named hand and foot meridian pointswere 13.6%, 17.6% and 19.6% respectively, while ID was 30.2% in patients, significantly higher than inhealthy people. For midnight-noon law, TCE relative to the reference points on the opening time was 1.25which was significantly higher than 1.08 before the opening time. The certain correlation (r = 0. 19,P < 0.01) between TCE and skin temperature and the increase after muscular exercise illustrate that TCE canindicate the energy metabolism level on meridians.CONCLUSION TCE is an ideal index to show the feature of acupuncture and meridians and may widely beused in the study and practice of traditional Chinese medicine.