Gold (III) forms a yellow coloured water soluble complex with diacetyl monoxime isonicotinoyl hydrazone (DMIH) reagent in acidic buffer pH 4.5 with ?max at 361 nm. The molar absorptivity and Sandell’s sensitivity are 1.50X10 4 L .mol -1.cm-1 and 0.00333 µg/cm2, respectively .The Beer’s law validity range is 0.985–11.82 µg/mL. The optimum concentration range is 1.97-9.85 µg/mL. Gold (III) forms (M:L) 1:1 complex with DMIH and stability constant of the complex is 3.263X106. The derivative spectrophotometric determination of Au (III) was carried out by measuring peak height method. The developed derivative spectrophotometric method was employed for the determination of gold (III) in synthetic alloy samples. The effect of various diverse ions was also studied.