A method involving the use of a reagent suitable for the rapid spectrophotometric determination of nitrites in water is described. Nitrites react with resorcinol in an acidic medium and the nitroso product forms a pale yellow chelate with the zirconyl ion. The absorbance of the chelate is measured at 347 nm and the calculated molar absorptivity is 2.67 × 10⁴ l mol^–1 cm^–1. The method is suitable for the determination of the nitrite ion in a 1.0-cm cell in the range from a few parts per hundred million to about 1 p.p.m. The relative standard deviation of the method is 1.5% at a concentration of 1 p.p.m. Some of the problematic interferents found in most of the analytical procedures for the determination of nitrites are tolerated in the present method. Features of the method include good selectivity and reproducibility, high stability of the coloured reaction product and simplicity.