The influence of different operation conditions (temperature, inlet acetylene concentration, and gas residence time) on the formation of soot from C2H2 pyrolysis has been studied. Pyrolysis experiments were carried out in a quartz reactor in the 1000−1200 °C temperature range, for different inlet C2H2 concentrations (15 000, 30 000, and 50 000 ppmv) and two gas residence times (1 706/T (K) and 4 552/T (K) s). Outlet gases were analyzed by gas chromatography, and the amount of soot produced was measured. The reactivity of the soot samples formed toward O2 was also studied. The results are supported by means of different soot characterization techniques: elemental analysis, determination of Brunauer−Emmett−Teller (BET) area, transmission electron microscopy, and Raman spectroscopy. A study of the influence of these operation conditions on the resultant soot oxidative reactivities has been carried out.