Boron was determined by atomic absorption spectrometry with a coated graphite furnace. Pyrolytic graphite tubes were first coated with titanium carbide, and then further coated with tungsten carbide. A mixture of nitrates of strontium and nickel and citric acid was then added to a sample solution as a matrix modifier. Using this doubly coated tube and this matrix modifier, the determination of boron was successful with high sensitivity. No interference from metal nitrates and chlorides was observed. The sulfate interference could be removed by adding ammonium salt of EDTA.