Refractory or hard sulfur found in a hydrocarbon stream containing refractory sulfur heterocycle compounds, particularly those exhibiting steric hindrance, is removed from the stream by contacting it with a sodium reagent comprising a sodium component, having free sodium, supported on a solid support component. If the hydrocarbon stream contains more labile or easy sulfur, then it is treated, typically by hydrodesulfurization, to remove at least most of the labile sulfur before it is contacted with the sodium reagent. This is useful for bringing the sulfur level of middle distillate fuel streams, such as diesel and jet fuel fractions, down to a level of less than about 10 wppm, employing conventional hydrodesulfurizing catalysts and conditions.