Optical coherence tomography (OCT) has become one of the most promising imaging techniques in biology and medicine. Microscopic techniques using rapid image acquisition by scanning beam techniques and large-sample macroscopic techniques using scanning-stages have been developed. Basic to all OCT imaging schemes described so far is the use of low coherence techniques to detect the depth position of light remitting sites in the object. Either time-domain OCT imaging or Fourier-domain OCT imaging can be used. Furthermore, OCT techniques have been developed for metrologic application s like the measurement of the refractive index of tissue and the velocity profile of fluids in tubes. This paper reviews OCT imaging techniques used in experimental and clinical applications and discusses arrangement s to improve longitudinal and transversal resolution.