This experiment was conducted to estimate the population density of stable fly (Stomoxys calcitrans L.) and to investigate the environmental factors affecting the seasonal fluctuation of the flies estimated from release-capture data by tagging method at Jae-Ju University, Suguipo, commenced from April, 1973. The results obtained are summarized as follows: Appearance of overwintering adults began to disperse in the field in about the middle of April and a high population density was observed from the end of May until September, and the population density was temporarily decreased during the summer season. It as mainly due to the rainfall and a typhoon. The dispersal times of overwintering adults were closely related with a change of temperature, that is the adult emergence took place on average minimum temperature of 11$^{circ}C$ and the grand surface tempo rature of 15$^{circ}C$.