The purpose of this study was to develop a reproducible, quantitative model of Candida albicans adhesion to human dentin through the use of a colorimetric method and to evaluate the effect of smear layer on candidal adhesion. Dentin disks with or without smear layer were incubated with C albicans (10 8 cells/mL) for 4 hours. After incubation, the disks were exposed to an (2,3)-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-(phenylamino)-carbonyl-2 H-tetrazolium hydroxide–coenzyme Q solution for 2 hours. The color of (2,3)-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-(phenylamino)-carbonyl-2 H-tetrazolium hydroxide formazan in the supernatant was determined spectrophotometrically at 492 nm. To relate formazan formation to cell numbers, standard curves were generated with known numbers of yeast cells without dentin. The number of adherent cells per square millimeter was then calculated. The number of attached C albicans cells was 2.4 × 10 4 per square millimeter in dentin with smear layer and 1.5 × 10 4 in dentin without smear layer ( P < .05). (2,3)-Bis(2-methoxy-4-nitro-5-sulfophenyl)-5-(phenylamino)-carbonyl-2 H-tetrazolium hydroxide assay is a potential microbiologic tool for the quantitative determination of Candida adhesion to human dentin.