A simple and sensitive spectrophotometric method has been developed for the determination of gold(III) using the newly synthesized reagent 3,5-dimethoxy-4-hydroxybenzaldehyde isonicotinoyl hydrazone (DMHBIH) in a neutral surfactant of Triton X-100 (5 %) (micellar medium). Gold(III) forms an orange coloured water soluble complex with the reagent in acidic medium pH 4.0. The molar absorptivity and Sandell's sensitivity of the coloured species are 1.14×10 5 l mol-1 cm-1 and 0.004587 µg/cm 2 , respectively. Beer's law is obeyed in the range 0.197-1.97 µg/ml of Au(III) at λ λ λ λ max at 386 nm. The developed derivative spectrophotometric method was satisfactorily applied for the determination of gold(III) in synthetic mixtures, certified reference materials, water samples and pharmaceutical samples.