Abstract: A method for simultaneous determination of mercury, selenium and arsenic in plant samples by atomic fluorescence spectrometry was developed. The samples were digested with HNO₃-HClO₄ and tributyl phosphate (TBP) was added for effectively eliminating foam, reducing memory effect and improving the accuracy. The method has been applied to the determination of trace Hg, Se and As in National Standard Reference Materials and the results are in agreement with certified values. The recovery test was satisfactory with precision (RSD, n=12) of 2.96%, 0.96% and 2.49% for Hg, Se and As, respectively.