Optical coherence tomography (OCT) is very promising for high-resolution cross-sectional imaging under-neath the surface of biological tissue. The axial resolution of OCT is determined by the coherence length of the light source used in a low coherence interferometer. In this paper, we review imaging characteristics of high-resolution OCT using broadband light sources as well as the coherence length. In the wavelength region of 0.8μm, a femtosecond laser and the thermal light source provides us the coherence length of a few micron or less using the bulk-optic interferometer. In the wavelength region of 1.3μm/1.5μm, a broadband fiber ASE and a supercontinuum light are useful for the high-resolution OCT under the condition where the wavelengthindependent fiber directional coupler is used.