Co-gasification performance of coal and petroleum coke (petcoke) blends in a pilot-scale pressurized entrained-flow gasifier was studied experimentally. Two different coals, including a subbituminous coal (Coal A) and a bituminous coal (Coal B), individually blended with a petcoke in the gasifier were considered. The experimental results suggested that, when the petcoke was mixed with Coal A over 70%, the slagging problem, which could shorten the operational period due to high ash content in the coal, was improved. It was found that increasing O2/C tended to decrease the syngas concentration and better operational conditions of O2/C were between 0.6 and 0.65?Nm3?kg-1. For the blends of Coal B and the petcoke, the slagging problem was encountered no more, as a result of low ash content in both Coal B and the petcoke. The better co-gasification performance could be achieved if the blending ratio of the two fuels was 50%, perhaps resulting from the synergistic effect of the blends. With the aforementioned blending ratio, the optimal condition of O2/C was located at around 0.65?Nm3?kg-1. The co-gasification was also simulated using Aspen Plus. It revealed that the simulation could provide a useful insight into the practical operation of co-gasification. Copyright (c) 2011 John Wiley & Sons, Ltd.