Daily shedding pattern and longevity of pollen are important consideration for the evaluation of gene flow of transgenic plants. During the day, the pollen shedding pattern of zoysiagrass was determined in the lawn by using a device to collect airborne pollen on a glass slide, resulting that the pollen grains were released predominantly between 7:00 and 9:00. The result was also supported by in vitro pollen germination test, which was performed with pollens collected from 1:00 through 24:00 at 1h interval. Influence of temperature and humidity on pollen longevity was determined by germinating pollen at 25°C after incubating them for 10, 30, 60, and 180 min under different temperatures and humidity with pollen of zoysiagrass that opened freshly at about 9:00. The result showed that pollen longevity of zoysiagrass was sensitive to change of temperature and humidity and longest under the temperture and humidity of 15-20°C and 80-99%, respectively. Under natural conditions with the same method as upper controlled conditions, was determined pollen longevity. Under sunny atmospheric conditions, pollen longevity decreased to 20% in 60 min, with a complete extinction in 120 min. Under cloudy atmospheric conditions, pollen remained viable up to 450 min, with about 20% longevity after 360 min. No significant difference was found between GM and non-GM plants in their pollen longevity.