A process for converting methane to higher molecular weight hydrocarbons comprises: (A) reforming methane by catalytic reaction with steam at elevated temperature to generate carbon monoxide and hydrogen; (B) subjecting the mixture of carbon monoxide and hydrogen to a Fischer-Tropsch reaction to generate one or more higher molecular weight hydrocarbons and water; and C) extracting or removing one or more oxygenates from the water.The oxygenates are either or both: on start-up of the process, catalytically combusted to provide heat for step (A), and replaced at least in part with methane from tail gas from step (B) when the temperature attains or exceeds the combustion temperature of methane; and/or used as a fuel-enhancer for tail gas from step (B) for steady-state heat provision in step (A).