Influence of time-on-stream (0.5-15 h), CH4/O-2 ratio in feed (1.8-8.0), space velocity (6000-510,000 cm(3) g(-1) h(-1)), catalyst particle size (22-70 mesh), and catalyst dilution by inert solid particles (diluent/catalyst weight ratio = 4) on the performance at different temperatures (600-900 degrees C) of the NiO/MgO solid solution deposited on SA-5205 [which is a low surface area macroporous silica-alumina catalyst carrier] in the oxidative conversion of methane to syngas (a mixture of CO and H-2) has been investigated. The dependence of conversion and selectivity on the space velocity is strongly influenced by the temperature. Both the conversion and selectivity for H-2 and CO are decreased markedly by increasing the CH4/O-2 ratio in the feed. The catalyst dilution resulted in a small but significant decrease in both the conversion and selectivity for H-2 and CO. The increase in the catalyst particle size had also a small but significant effect on both the conversion and selectivity in the oxidative conversion process. Both the heat and mass transfer processes seem to play significant roles in the oxidative conversion of methane to syngas at a very low contact time or very high space velocity (5.1 x 10(5) cm(3) g(-1) h(-1)).