Abstract Unmigrated reflection seismic energy recorded at the earth's surface, for example in the form of common-offset records, often provides a remarkably coherent picture of subsurface structure. Coherent as it might be, however, this picture is not correct, suffering from several distorting effects, most notably those of diffraction from geologic bed truncations and lateral movement of the energy between the reflection points on dipping beds and the surface locations. Seismic imaging is the process that corrects these distortions. In the next paragraphs, I discuss this important technology.