The effects of furnace temperature and residence time on the mean primary particle diameter and aggregate shape of carbon black are investigated by benzene pyrolysis to confirm the factors that control the configuration of carbon black. With a high furnace temperature and short residence time, the mean primary particle diameter decreases and the aggregate shapes are complex; on the other hand, with a low furnace temperature and short residence time, the mean primary particle diameter increases and the aggregate shapes are simple. Moreover, with a high furnace temperature and long residence time, the mean primary particle diameter increases and the aggregate shapes are relatively simple. However, the aggregate shapes remain basically unchanged with increasing residence time. The results of this study suggest that the main factors that control the configurations of carbon black are nucleation, surface growth and sintering of primary particles. Nucleation, which is affected by high-molecular-weight polycyclic aromatic hydrocarbons (PAHs), controls aggregate shapes, while surface growth, which is affected by low-molecular-weight PAHs contributes to the growth of primary particles. The sintering of primary particles controls the simplification of aggregate shape and the growth of primary particles. (C) 2012 Elsevier B.V. All rights reserved.