A very sensitive and selective spectrofluorimetric method has been developed for nickel (ΙΙ) determination in environmental samples. The method is based on measuring the decrease in fluorescence intensity of murexide after nickel (ΙΙ) binding. The intensity of the fluorescence emission peak was measured at ex/em 345/431 nm in several solutions with pH interval 3.0-7.0. The fluorescence intensity decrease was found to be linear in the concentration range of 0.007 mg.L(-1) to 0.1 mg.L(-1) and 0.1 mg.L(-1) to 20 mg.L(-1) of nickel (ΙΙ) by using 10(-4) M murexide at pH 3. The detection limit was found 0.004 mg.L(-1). Relatively large excesses of over 20 cations and anions do not interfere. The method was successfully applied to the analysis of nickel (ΙΙ) in sea, rain and ground water. This method is very precise and accurate (R.S.D. = 0.42% for the determination of 0.05 mg.L-(1) nickel in 10 replicates).