Abstract Line spectra of vanadium, niobium, titanium, molybdenum and rhenium of sufficient intensity to allow detection at the 1–10 p.p.m. level can be excited in fuel-rich, oxy-acetylene flames. For the strongest lines of tungsten, the sensitivity of detection is 90 p.p.m. Weak lines of zirconium, hafnium, osmium, tantalum and uranium are also observed in these flames. Recordings of the spectra are given along with wavelength tables of the strongest lines.