The present paper reports a comparative analysis of sigma 3 (in the coincidence site lattice notation) grain boundary types, in two grain boundary engineered brass specimens, by use of electron backscatter diffraction (EBSD) data coupled to the measurement of boundary traces in a single section. Although most of the data were analysed using the new single-section technique, an analysis of boundary plane orientations in three dimensions was made in a subset of the data in order to validate the single section methodology. The single-section trace analysis procedure. coupled with EBSD, is a viable and robust tool for analysis of sigma 3 grain boundary planes. The procedure provides data which suggest that part of the enhanced strain-to-failure in specimen B compared to specimen A is the result of an increased proportion of mobile sigma3 boundaries, i.e. those which are displaced from the [111] symmetrical tilt configuration.