The food coloring amaranth (F, D and C red No. 2) and the red pigment carmine, but not erythrosine (F, D and C red No. 3), caused a twofold enhancement of two enzymes (aryl hydrocarbon hydroxylase and guanylate cyclase) that have been linked with chemical carcinogenesis. Dose response relationships revealed that carmine enhanced both enzymes to near maximal levels at concentrations as low as 1 to 10 nM while amaranth needed a concentration of 100 nM to cause a maximal enhancement. These data suggest that amaranth and carmine mimic the effects of some chemical carcinogens at the cellular level, but erythrosine does not mimic any of these effects.