Abstract: New, sensitive and simple methods for spcctrophotometric determination of platinum(Ⅳ) with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) and for simultaneous determination of palladium(Ⅱ ) and platinum( Ⅳ ) based on the difference in temperature required for complex formation reactions between the two metal ions and 5-Br-PADAPhave been respectively developed. On adding nonionic surfactant polyethyleneglycol octylphenylester (OP), the colour of Pd(Ⅱ)-5-Br-PADAPcomplex in the aq. medium become very stable; the formation reaclion of Pl( Ⅳ )-5-Br-PADAPcomplex was greatly accelerated and the sensitivity of this colour rcaction enormously increased. 35 common foreign ions do not interfere with the simultaneous or respective determination of Pd( Ⅱ ) and Pt(Ⅳ). The coefficients of variation are 0.14-3.6% (n=5). Good recoveries (97-109%) of palladium( Ⅱ ) and platinum(Ⅳ) in the mixtures were obtained without any separation or masking.