A rapid spectrophotometric method for the determination of low levels of cobalt(III) with 2,2 -dipyridyl ketoxime is proposed. A 3:1 water-soluble complex which is easily extractable into chloroform and has an absorption maximum at 388 mmicro forms instantaneously. Beer's law is obeyed and the molar absorptivity is 19.5 x 10(3). An investigation of the interference of 60 cations and anions shows the method to be widely applicable; it is simple, convenient and reproducible.