AbstractObservations are reported on the laser surface alloying of commercial purity (CP) Ti and Ti–6Al–4V alloy with carbon and of CP Ti and Ti–15 Mo alloy with nitrogen. Repeated laser melting of substrates precoated with Dag graphite was used for carbon alloying, while alloying with nitrogen was done by laser melting in a nitrogen flow. Structural studies included X-ray diffraction and electron microscopy. Both alloying procedures produce hardened surface layers up to∼650 HV using carbon and>∼1000 HV using nitrogen. This hardening resulted from the formation of TiC and TiN respectively, including primary dendritic carbide and nitride.