Fullerene mixture of C-60 and C-70 was produced in gram quantities in a solar reactor using partially (50 kW) the power of the 1 MW CNRS solar furnace at Odeillo. Fullerene yield was studied as a function of buffer gas (helium and argon), pressure (in the range 80-500 hPa) and gas flow rate. Mean Fullerene yield of 13.5% was measured with helium at 450 hPa and 10 sm(3)/h, at a carbon vaporization rate of 21 g/h. This mean value refers to three samples collected inside the experimental set up; the maximum yield for one single sample (inside the reactor) was 16%. The dramatic effect of pressure and gas flow rate on the process selectivity is correlated to the dilution number (number of carbon atoms versus number of buffer gas atoms) and to the results of a numerical simulation related to the temperature distribution in the annealing zone of the reactor. (C) 2004 Elsevier Ltd. All rights reserved.