Etching of synthetic and natural diamond single crystals has been carried out in KNO3 or NaNO3 melts at 600-900 degrees C. A correlation between the etch pits and dislocations emerging on the {111} faces has been established by the etching of oppositely matched cleavages, thin plates, natural diamond crystals with trigons on the octahedral faces and repeated etching. The etching results were correlated with X-ray topography data. It has been revealed that pyramidal etch pits on the {111} diamond faces with the inclination angles of 2-8 degrees are formed at the emergence points of dislocations. In this case, the etch pits with the inclinations of 5 degrees, 6 degrees, 5 degrees and 8 degrees originate at the emergence points of edge dislocations, more shallow pits are probably related to screw and partial dislocations. The etch pits with the inclination of 11-15 degrees are not associated with dislocations and can be related to impurity clusters, microcracks and other surface defects. (c) 2006 Elsevier B.V. All rights reserved.