The use of nebulized spray pyrolysis for the synthesis of carbon nanotubes has been investigated in detail. Multi-walled carbon nanotubes (MWNTs) with fairly uniform diameters and aligned MWNT bundles have been obtained by using solutions of organometallics such as ferrocene in hydrocarbon solvents. The well-graphitized MWNTs were obtained with a solution of ferrocene in xylene. Single-walled nanotubes (SWNTs) were obtained when cobaltocene or nickelocene is used along with toluene. Fe(CO)5 in mixture with acetylene also yielded aligned MWNT bundles. The procedure described can be scaled up for large-scale production. (C) 2004 Elsevier B.V. All rights reserved.