The observed specificity of enzymes is affected by the reaction medium and can be, at least partly, explained by a change in substrate solvation. By using a transfer free energy method, enzyme kinetics in an organic solvent can be corrected to a chosen standard state. The choice of standard state does not affect conclusions about a single substrate. However, when two or more substrates are compared, the "corrected specificity" becomes a function of the standard state. To illustrate this, we have studied the esterification of sulcatol and several saturated fatty acids catalyzed by Candida rugosa lipase. The observations in toluene (based on V-m/K-m) show a preference for C4, C8, C10, and C12 fatty acids. Correction to the pure liquid standard state suggests more or less the same specificity. But corrections to the gas phase or dilute aqueous standard states would suggest a strong preference for longer-chain fatty acids. Hence, such corrected specificities should be used and interpreted only with great care.