A simple and selective spectrophotometric method for the determination of trace amounts of selenium(IV) is described based oil the oxidation of phenylhydrazine-p-sulphonic acid and coupling reactions. Selenium(IV) oxidizesphenylhydrazine-p-sulphonic acid into its diazonium salt in all acid medium. The diazonium salt is then coupled with acetylacetone or ethylacetoacetate in all alkaline medium, which gives azo dyes with absorption maximum at 490 or 470 nm, respectively. The method obeys Beer's law in the concentration range of 0.5-20 mu g mL(-1) of selenium with phenylhydrazine-p-sulphonic acid-acetylacetone and 1-24 mu g mL(-1) of selenium with phenylhydrazine-p-sulphonic acid-ethylacetoacetate couples. The molar absorptivity, Sandell's sensitivity of the systems with phenylhydrazine-p-sulphonic acid-acetylacetone and phenylhydrazine-p-sulphonic acid-ethylacetoacetate couples were found to be 1.02x10(4) Lmol(-1) cm(-1), 7.69x10(-3) mu g cm(-2) and 1.18X10(4) L mol(-1) cm(-1), 6.67x10(-3) mu g cm(-2), respectively. The developed method has been successfully applied for the determination of selenium in plant material, water and soil samples.