This outline survey of indoor and outdoor radon concentrations in five major cities in Korea was carried out with Electrostatic Integrating Radon Monitor(EIRM) from February to December, 1996 and January to december, 1998. The mean indoor and outdoor radon concentrations in five major cities in 1996 were $21.9{;}Bq/ extrm{m}^3$ and $9.6{;}Bq/ extrm{m}^3$, respectively. The mean indoor and outdoor radon concentrations in 1998 were $20.8{;}Bq/ extrm{m}^3$ and $9.0{;}Bq/ extrm{m}^3$, respectively. These were below the U.S.EPA radon action level. The range of indoor to outdoor radon concentrations were $0.8{;}Bq/ extrm{m}^3{;}~{;}45.6{;}Bq/ extrm{m}^3$ in 1996, $0.5{;}Bq/ extrm{m}^3{;}~{;}15.2{;}Bq/ extrm{m}^3$ in 1998, respectively. The result of our analysis showed that radon concentrations in indoor air were clearly higher than those in outdoor air. Inspection of seasonal distribute pattern indicates the enhancement during winter relative to summer.