The purpose of this study was to evaluate the needles used for epidural anesthesia. Medical doctors feel resistant force when inserting needles into the epidural space, and resistance diminishes after puncturing the ligamentum flavum, but the relationship between the resistant force and the puncture of the ligamentum flavum is not known. We conducted a comparative study using porcine ligamentum flavum. Porcine spine from a slaughterhouse was divided into thoracic (n=11) and lumbar (n=17) spine, and test pieces were fixed by RTV rubber. A needle and a load cell were set on a motorized stage, and the speed of insertion was set at 2 mm/s. A CCD camera recorded the images during the puncture of the ligamentum flavum. Two needles were employed; one was a sharp (tip angle of 25 degrees), the other was a dull (tip angle of 38 degrees) . The results showed that the ligamentum flavum deformed before the needle puncture. The peak value of force (Fp), drop of force (Fd), and deformation of the ligamentum flavum were compared by Student-Newman-Keuls test. Fp and Fd of the lumbar spine were higher than the thoracic spine (p<0.01) . Fp and Fd of the sharp needle were lower than those of the dull needle (p<0.01) . The difference in the deformation was not significant between the two types of spine and the two types of needle. Our conclusions are that 1) the ligamentum flavum deforms up to 3 mm before puncturing; 2) the lumbar spine shows a higher resistant force; and 3) the insertion resistance of the dull needle was 30% higher than that of the sharp needle.