The particle size of suspended particulates was measured by a Anderson air sampler from Mar. 1982 to Feb. 1984 in a part of Seoul. It was concluded as follows : 1) The arithmetic concentration of suspended particulates was $147.8{mu}g/m^3$ in Spring, 136.9 in Summer, 131.9 in Autumn and 158.1 in Winter respectively. 2) The cumulative distribution of suspended particulates size in logarithmic diagram showed similar to normal log distribution. 3) The atmospheric particulate matters showed a bimodal size distribution on the base of unit particle concentrations, which divided at approximately $2{mu}m$ in the diameter. 4) While the fine particulates less than $2.1{mu}m;was;35.4{sim}45.0%$, the coarse particulates was $55.0{sim}64.5%$. 5) The higher the concentration of suspended particulates, the more increased the ratio of fine particulates. The higher the concentration of suspended particulates, the lower median size of suspended particulate as well. 6) The respirable dust particulates less than $4.7{mu}m;was;52.2{sim}62.9%$ in seasonal average through the 2 year samples. With the above result, air pollution concerned with public health could be evaluated and the control measures also are suggested.