A semi-automated method for the determination of antimony in geological materials involves the following steps. After a manual digestion of the sample with a mixture of concentrated sulfuric, nitric, and perchloric acids, the sample is brought to volume with 10% hydrochloric acid. The sample is then mixed in a continuous flow-automated sequence with reducing agents, further acidified with hydrochloric acid and reacted with a solution of sodium borohydide to form the gaseous hydride of antimony. The resulting gas mixture of hydrogen and hydrides is decomposed in a heated quartz tube in the optical path of an atomic absorption spectrophotometer. The amount of antimony present is proportional to the absorbance, measured by peak height.Interferences that exist are minimal and most geological materials can be analyzed directly. The relative standard deviation (RSD) of the digestion and the instrumentation is <2%. The blank-limited detection limit is 0.2 yg/L (microgram/Liter) and the sensitivity is 0.44 vg/L antimony.