Interfacial phenomena and reaction kinetics between the ironmaking slag and various cokes or graphite were investigated at 1327-1500 degrees C using the sessile drop method. The slag-coke and slag-graphite contact angles were found in a range of 101-122 degrees and 94 degrees, respectively. The contact area was in a range of 0.52-1.21 cm(2) g(-1) of slag for slag droplets of 0.9-1.6 g, contacting various carbon types. The rate of FeO reduction by coke was less than half of that by graphite and increased with an increasing temperature and FeO content in the slag. The reduction of SiO2 was suppressed by the FeO present in the slag. The significant differences in the reduction rate by different cokes were observed, and the ash yield by cokes was found to be responsible for these differences. The ash presented at the slag-carbon interface would either retard the mass transfer of FeO from slag bulk to the interface or reduce the effective slag-carbon contact area. The effects of coke crystallite size, anisotropic carbon content, minerals, and maceral of original coal of the coke on the reduction rate were examined; correlations between these coke parameters and the reduction rate were found to be insignificant.