A model is presented for the interpretation of magnetometer data in terms of archaeological features beneath the ground. It describes the detector's response to the assemblage of buried features, incorporating both a spread function and a statistical error process as well as appropriate prior beliefs about the nature of archaeological features. The problem is to estimate the magnetic susceptibility of the buried features at each horizontal location. Pseudo-likelihood is used to estimate the prior parameters and the OSL algorithm to nd the MAP estimates of the susceptibili-ties. The approach is illustrated with both simulated data and measurements from an archaeological site. In the latter case, the reconstruction of the buried features corresponds well with the archaeologist's observations during subsequent excavation.