The first crustal-scale controlled source seismic refraction experiment in the southern Korean Peninsula, KCRUST2002, was carried out along a 300-km long profile across this peninsula in December 2002. Iterative processing and modeling produced a laterally varying layered crustal velocity model. The crust is thickest (34 km) below the Okcheon fold belt in the middle of the transect and thinnest (28 km) at the eastern end where the Cretaceous Gyeongsang basin is characterized by 5 km of low velocity material that constitutes the upper crust. The P velocities in upper and lower crust range from 5.4 to 6.0 km/s and from 6.4 to 6.7 km/s, respectively. The average crustal Poisson's ratio is found to be 0.25--0.27 (Vp/Vs = 1.73-1.78) along the profile. A mid-crustal velocity discontinuity is recognized in the northwestern part of the transect. The underlying mantle has velocities in the range of 7.9--8.1 km/s.