The wetting and bonding behaviour between diamond plaques and copper alloyed with chromium, titanium or vanadium has been studied using the sessile drop technique. Wetting was induced at 1150° C by additions of more than 0.1 at. % of titanium, but additions of vanadium up to and beyond the solubility limit did not cause wetting to occur. The room temperature strengths of the interfaces between the diamond plaques and the solidified sessile drops increased with increasing alloying element concentration, reached a maximum value at a concentration less than that needed to induce wetting, and thereafter decreased. The maximum strengths achieved by alloying with chromium, titanium or vanadium were 35.5, 42.0 and 69.8 kg mm−2 respectively. The reactivity of the alloyed sessile drops was assessed using metallography, EPMA and a surface contour device. A tentative picture of the effects of diamond-metal interactions on wetting and bonding behaviour was developed.