Description: This article discusses the effects of O2, H2, and N2 gases on the field emission properties of diamond-coated microtips. Abstract: We report the effects of O2, H2, and N2 residual gases on the field emission properties of uncoated and diamond-coated individual Mo microtips. The microtips are made using electrochemical etching techniques and positioned 5 µm from the anode using a scanning tunneling microscopy system. The authors observe that the field emission (FE) current and turn-on voltage of diamond-coated microtips are significantly less degraded by O2 exposure that those of uncoated Mo microtips. H2 exposure enhances the FE properties of both uncoated and diamond-coated microtips, while N2 exposure does not have any significant effect.