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in Wiley InterScience (www.interscience.wiley.com).Multi-walled carbon nanotubes (MWCNTs) have been produced with high selectivity by fluidized bed catalytic chemical vapor deposition from ethylene on Fe/Al 2 O 3 catalysts. The influence of operating parameters such as deposition duration, temperature, ethylene and hydrogen partial pressures, and iron loading on MWCNT productivity, process selectivity, characteristics of final powders, and chemical composition of the outlet gases has been analyzed. Using gas phase chromatography, methane and ethane have been detected, whatever are the conditions used. Between 650 and 7508C, no catalyst deactivation occurs because nucleation remains active all along the synthesis, thanks to the explosion of the catalyst grains. Above 6508C, ethane itself produces MWCNTs, whereas methane does not react in the temperature range, 550-7508C. The formation of MWCNTs induces marked bed expansions and sharp decreases of grain density. Apparent kinetic laws have been deduced from the collected data. The apparent partial orders of reaction for ethylene, hydrogen, and iron were found to be 0.75, 0, and 0.28, respectively.