A total of 69 dyes were incorporated separately at different concentrations into an agar medium for evaluation of their effects on the quantitative recovery of five serotypes of Yersinia enterocolitica. One strain of Pseudomonas aeruginosa and one strain of Bacillus cereus were included for comparative purposes. Certain dyes were evaluated further for their selective properties with five additional serotypes of Y. enterocolitica, three strains of P. aeruginosa, and two of Engerobacter spp. Metanil yellow was the only dye which was tolerated bettr by Y. enterocolitica than by P. aeruginosa. Dye sensitivity was variable amond strains of the same serotype of Y. enterocolitica. In general, Y. enterocolitica showed a tolerance to dyes greater than that of gram-positive bacteria and similar to that of other gram-negative bacteria.