Concentrations of ammonia (NH3), hydrogen sulfide (H2S) and methyl mercaptan (CH3SH) are high in the air above landfills in Taiwan. Odors are strong and many flies are present. These factors were studied in the air above selected landfill sites where odor was considered to be a nuisance. In this study, Natural Effective Microorganisms Enzyme (NEME) was sprayed on selected sampling sites to reduce the odor, the concentration of NH3, H2S and CH3SH and the number of flies in landfills. The odor levels, the concentrations of NH3, H2S and CH3SH and the numbers of flies at various sampling sites before and after spraying with NEME were discussed. Results revealed that at the Tian-Wai-Tian Landfill in Ji-Long City, after NEME was sprayed, the measured odor level ranged from 190 to 552, and the reduction ratios were 99.4%. At the Yan-Pu Country Landfill, after it was spraying with NEME, the measured odor level had a mean of 1360 and the reduction ratio had a mean of 71.6%. At the Ping-Tung Municipal Landfill, after it was sprayed with NEME, the measured odor level had a mean of 602 and the reduction ratio averaged 68.1%. The reduction ratio of NH3 from landfills averaged 72.2% and 61.1% at the Yan-Pu Country Landfill and the Ping-Tung Municipal Landfill, respectively. However, both before and after spraying with NEME, the measured H2S and CH3SH concentrations at both the Yan-Pu Country Landfill and the Ping-Tung Municipal Landfill were under 0.03 ppm. The reduction ratio of the number of captured flies averaged 55.0% and 39.7% at the Yan-Pu Country Landfill and the Ping-Tung Municipal Landfill, respectively.