Coking has presented difficulties in reactions including pyrolysis and steam has been added to reduce coking. In this study, the effect of steam on coking in the pyrolysis of naphtha components was studied thermodynamically and experimentally for non-catalytic tubular reactor systems. The qualitative relations between these two thermodynamic and experimental studies were established. In both studies coking was reduced as the steam ratio increased. However, experimental studies indicated that the reduction was more effective for smaller values of the ratio, leading to an effective ratio of about 0.5, and that weak coking still occurred for the ratio greater than the thermodynamic zero-coke ratio.