The formation of stibine during the electrolytic reduction of aqueous antimony solutions has been investigated. Using a lead cathode, the rate of stibine formation is independent of temperature, current density, and stirring rate, but increases as a direct function of total current and pH. Stibine is formed 1.8 times more rapidly from Sb III than from Sb V solutions (in ). Cathode materials are without effect except mercury and porous graphite which gave higher rates of stibine formation. The process probably takes place in two main stages: the deposition of antimony metal; the reduction of this metal to stibine. When the antimony concentration is the cathode is well covered with antimony, and the second stage is probably rate controlling. When the antimony concentration is the first stage is probably the slowest step.