Most anomalies encountered in ground and airborne magnetic surveys are caused by rock and/or ore masses whose shapes are either dike-like and sheet-like structures of infinite length or limited parallelepipedoidal prisms of varying dips, widths, lengths, and depths of burial of the top and bottom faces. The quantitative interpretation problem consists essentially in determining all of the above parameters through a complete analysis of the field profile. Our research group has discovered new methods with which to perform this interpretation. These techniques are both analytically correct and very fast.First, the field profile is decomposed into its symmetrical and antisymmetrical components by a new method that uses arbitrarily chosen conjugate points. Our procedure does not require any previous knowledge or assumption of the zero datum level or of the center of the body.Second, the symmetrical and antisymmetrical components of the field profile are analyzed separately. In the case of dike or bed-like structures, the entire procedure takes but a few minutes and requires a single set of six master curves.The case of the interpretation of parallelepipedoidal prisms is still under study and will be presented shortly in a second paper.