The fundamental computation equations for dip shooting are reviewed. From a consideration of the curvature of the wave front of the reflected wave an expression is derived for the angle of arrival in terms of the reflection time difference over a finite spread. The effect of curvature of the reflecting bed is discussed. An outline is given of a rigorous computational procedure which takes full consideration of the three dimensional aspect of seismic interpretation and which is based on the use of time cross-sections and maps. Since this procedure is presented on the basis of a velocity equation which is a function only of depth, it is indicated that a modification must often be made to account for the deviation of the direction of velocity gradient from the vertical.