On the basis of spatial covariance, it is found that, by spatial filtering the localisation of a single dipole source, both parallel and perpendicular to the measurement plane (assuming a signal-noise ratio of 5∶1), can be performed with an accuracy of <0.5 mm. When the singal-noise ratio is increased to 30∶1, the resolution of temporally independent current sources separated by 2 mm becomes practicable. This resolution study is carried out by means of a pair of unity current dipoles with the dipole distance as a varying source model parameter. The conclusions, drawn from the results of computer simulation and supported by statistical calculations, refer to the spherical model of the volume conductor of the brain.