Purpose: To investigate the microbial adherence to the surfaces of a nonprecious metal alloy after plasma nitriding. Materials and Methods: The plasma-nitriding process was performed to the surfaces of metals prepared from a nickel-chromium alloy. The microorganisms were labeled with technetium-99m. After the labeling procedure, 60 metal disks were treated with a microorganism for each use. Results: The results revealed that the amount of adherence of all microorganisms on surfaces was changed by plasma-nitriding process; adherence decreased substantially (P < .05) and the differences in plasma nitriding time were not significant (P > .05) Conclusion: With the plasma-nitriding process, the surface properties of nonprecious metal alloys can be changed, leading to decreased microbial adherence. Int J Prosthodont 2006;19:202–204