The Incheon bridge will be an exemplary example of a cable-stayed offshore bridge located in the Rep. of Korea. It connects the Songdo city to the Incheon International Airport. Pile foundation of Incheon bridge is consisted of large diameter drilled shafts, up to 55m deep and 3.0m in diameter, which were embedded in rock. This paper describes the load distribution and deflection of drilled shafts subjected to lateral loads in marine clay. The emphasis was on quantifying the cyclic lateral soil resistance placed from the piles to surrounding soils based on one-way and two-way cyclic loading tests performed on small and full-scaled drilled shafts. The cyclic loading tests included four test piles founded in weathered and soft rocks through soft clay and silt: three of the test piles (LTP-1, LTP-2, LTP-3) were the small-scale driven piles (diameter= 1.016m, length=26m); the other (LTP-4) was the full-scale drilled shaft (diameter=2.4m, length=45m). All test piles were performed by the one-way loading method except for LTP-3 (two-way). Based on the test results, lateral cyclic behaviors of offshore drilled shafts in marine clay are discussed and compared with existing methods.