The magnetic total field anomaly is considered as the convolution of two analytically determined functions. One of them is chosen such that it modifies the amplitude of the anomaly while the other controls the anomaly pattern. Using the anomaly of vertical-sided finite prisms, the inverse of the shape function is computed in the Wiener mode. This is an optimum filter operator, in the least-square sense, to be convolved with the data.The majority of the structures which are the targets of exploration at archaeological sites can be represented as assemblages of vertical-sided prisms. This fact motivates the selection of the basic model. On that basis the filtering scheme results in anomalies centered at the epicenter of the disturbing bodies, delineates their lateral extent fairly well, and gives a measure of their magnetization.Applications of synthetic and actual data clarify the merits and disadvantages of the technique.