The kinetics of alcohol oxidation catalyzed by the enzyme horse liver alcohol dehydrogenase (HLADH) is studied in water/alcohol/C12E23 systems with a series of n-alcohols ranging from ethanol to I-decanol or with alpha,omega-alkandiols, namely, 1,5-pentanediol and 1,7-heptanediol. Essentially, the water-rich part of the ternary systems is examined, either without C12E23 or at several constant C12E23 concentrations above the cmc (1, 8, and 22 mass %). The substrate inhibition of the enzyme allows one to infer alcohol partition coefficients between the outer aqueous pseudophase and the surfactant aggregation pseudophase. In the case of short-chain n-alcohol (ethanol, I-propanol) and alkandiol (1,5-pentanediol) systems, the alcohol seems to remain in the aqueous pseudophase, whereas in the case of middle- and long-chain n-alcohol (1-butanol to 1-decanol) and alkandiol (1,7-heptandiol) systems, the alcohol participates in the structuration of the micelle.