Deposition of diamond on tungsten wires were tried by means of cyclic thermal plasma chemical vapor deposition. Deposition rate, morphology, and uniformity were found to be strongly dependent upon the wire size and its heating history estimated using a simple model based on the heat balance equation. Relatively uniform coatings were obtained on wires with a diameter of 0.2 mm at a rotation speed of 450 rpm. This was not the case with larger wires with a diameter of 0.7 mm at 200 rpm. This effect is attributed to the disturbance of the flow pattern around the large wire. Under the best conditions, 1 &mgr;m uniform highly quality diamond film could be deposited on 0.2‐mm‐diam tungsten wires over a total run time of 75 min. The corresponding depositing duty time is calculated to be about 2 min. ©1995 American Institute of Physics.