Chemical Laboratory, Regional Centre for Exploration and Research, At,mio Minerals Division, Department of Atomic Energy, Shillong-793 012 Manuscript received 10 June 1988, accepted 14 December 1988 A new colour reaction for the determination or nitrite in water is reported. Nitrite reacts with p-aminophenylmercaptoacetic acid in hydrochloric acid medium to form a diazonium cation, which is subsequently coupled with 8-hydroxyquinollne in alkaline medium to produce a reddish orange azo dye. The reactions are very fast and require no control of temperature. Features or this method Include good sensitivity, rapidity, reproducibility, freedom from pH effects, temperature independence, less interference and ease or performance.