This method is for determining cyanide in aqueous solutions in the presence of large quantities of sulfide. The lower limit of detection in the presence of 1.0% or 0.1% sulfide is 0.2 or 0.02 mass-ppm cyanide, respectively. The upper limit of detection can range from 200 ppm to 10,000 ppm cyanide depending on the size of the sample selected for analysis. Thiosulfate above a level of 0.1% will interfere with the test. Significant amounts of sulfite, thiocyanate, aldehydes, amines and other materials can also interfere with the analysis. The instability of cyanide in the presence of air requires that the analysis be performed as soon as possible after sampling.