The synthesis of single-walled carbon nanotubes (SWNTs) in sooting flames is reported. This method offers a viable path towards low-cost large-scale synthesis, which is lacking in arc- and laser-based SWNT synthetic techniques. As with other methods, the growth of the SWNTs in the flame is catalyzed by the presence of metals. Iron and nickel were introduced into the flames by subliming their bis(cyclopentadienyl) derivatives into an inert gas feed line that, mixes with the hydrocarbon fuel and oxygen at the burner surface. Acetylene and ethylene are both suitable fuel choices for SWNT synthesis. While no SWNTs could be detected when benzene was used as the fuel, long metal-filled multiwalled nanotubes (MWNTs) with many defects were abundant. The effect of the fuel's chemical identity is discussed within the formation mechanisms for vapor-grown carbon fibers (VGCFs), SWNTs, MWNTs, and fullerenes.