The purpose of this study was to compare the size of biopsy cores obtained using a biopsy needle before and after manual curving of its inner stylet.A total of 40 open renal biopsies were randomly performed on two ex vivo beef kidneys using four different semiautomated cutting needles. Two 18-gauge and two 20-gauge needles were used; one needle of each gauge had its inner stylet manually curved. Ten biopsy specimens were obtained using each needle and then were put into four different formalin containers, one for each needle, and sent to the pathology laboratory. Two pathologists who were blinded to the corresponding needles reviewed the samples in consensus and measured the dimensions of obtained cores.The mean diameter of the cores was larger when curved needles were used: for the 18-gauge needles, the core diameters were 0.866 mm for the curved needle and 0.688 mm for the straight needle, and for the 20-gauge needles, the core diameters were 0.522 mm for the curved needle and 0.480 mm for the straight needle. The length of the samples was also longer when they were obtained using the curved needle. When we considered the cores as cylinders, the calculated volumes of samples obtained using the curved needles were significantly larger.Manually curving of the inner stylet of the cutting biopsy needle results in larger cores, in terms of diameter and length, and results in significantly larger overall volume.