The color reaction between Xylenol orange (XO), zirconium (IV) and fluoride ions in the presence of various surfactants alone or in combination was studied at various pH. The XO -zirconium)IV)-fluoride ion ternary complex in mixed micellar media containing a low concentration of N-hexadecylpyridinium chloride (HPC) as a cationic surfactant and large amounts of (poly{oxyethylene)dodecyl ether (Brij 35) as a nonionic surfactant at weakly acidic media was found to be the most stable, and showed a remarkable bathochromic shift and clear contrast against a reagent blank. The maximum absorbance was at 600 nm in the mixed micellar media at pH 3.5, and the apparent molar absorptivities at 600 nm were 7.0 × 1041 mol−1cm−1for zirconium(IV) and 1.4 × 1041 mol−1cm−1for fluoride ion. The calibration curves covered the ranges of 0.5 ∼ 20.0 μg/10 ml zirconium! IV) and 0 ∼ 20.0 μg/10 ml fluoride ion with the Sandell sensitivities being 0.0013 μg/cm2for zirconium(IV) and 0.0016 μg/cm2for fluoride ion.