Scanning tunneling microscopy (STM) observations made on pBR322 DNA are compared with methods known to give information on DNA intrinsic curvature : polyacrylamide gel retardation, electron microscopy and computer modeling. It is concluded that STM is a powerful method for studying DNA structural features. Moreover, it is the only method to reveal simultaneously nanometric scale detail and long-range information. Use of STM for analyzing fine DNA structural features in regions involved in gene regulation should make an important contribution to genetics.