Titanium diboride can be produced by ball-milling a mixture of TiO2, B2O3, and Mg metal for between 10 and 15 h. The reaction was found to be completed during the milling with no evidence of residual Mg. The unwanted phase, MgO, was readily removed by leaching in acid. The leached powder obtained after 15 h milling had a particle size of <200 nm and was highly faceted. The particle size decreased to similar to 50 nm after 100 h milling and seemed to be relatively monodisperse. Scherrer calculation of the crystallite size showed that the product particles were probably single crystal.