Imported and domestic benzidine (92875) dyes were studied for residual benzidine. Thirty three imported samples of benzidine derived dyes from eight countries (Egypt, France, Holland, Poland, Belgium, Romania, Korea and India) were analyzed randomly. A representative portion of each dye was extracted to retain the free benzidine in the sample. Twenty six domestic samples of benzidine derived dyes produced by three United States companies were also analyzed. The imported samples showed considerable variation in free benzidine, ranging from less than 1 part per million (ppm) to 1254ppm with an average of 64ppm, a median of 6, and a standard deviation of 219. There was no correlation between the residual benzidine found in imported dyes, the color, or the exporting country. In the domestic samples, the free benzidine ranged from 1 to 270ppm (25 dyes contained 20ppm or less) with an average of 16ppm, a median of 3.5, and a standard deviation of 52. The authors conclude that the imported dyes contained slightly greater amounts of benzidine than the domestic dyes. They suggest that possible dye impurities that are present during the manufacture and use of all synthetic organic dyes be considered when evaluating their carcinogenic potential.