Thermogravimetric analysis was used to study the pressure effect on the activation energy during asphaltene gasification. The experiments were carried out under steam atmosphere at different pressures (1-80 bar) and temperatures (100-900 degrees C). The measured values of the total mass loss of asphaltenes are pressure dependent. They increase with rising pressure. Kinetic parameters were determined using a first-order kinetic model and integral method with thermogravimetric analysis data. The activation energy was found to vary from 189.6 to 130.4 kJ/mol and frequency factor from 4.1 x 10(10) to 1.2 x 10(6) min(-1). A decrease of both parameters was observed with an increasing pressure. Coke produced during the gasification is obviously characterized by the bigger pore size and weaker mechanical strength as the pressure increases from 1 to 80 bar. The structure of the produced coke becomes more crumbly with raising pressure. The formation of spherical carbon particles with a radius of around 5 mu m was observed at high pressure (20-80 bar). The elemental composition of these particles is roughly equal: C (similar to 97%), S (similar to 2%), and 0 (similar to 1%).