The binding constants (log K) of eugenol, o-ethoxy-benzoic acid, and their analogues, plus other organic compounds widely used in dentistry with bovine serum albumin, were examined with respect to the partition coefficients of these compounds in octanol-water (log P). Linear relationships between log K and log P values were obtained with high relative coefficients. Eugenol and o-ethoxybenzoic acid showed a relatively large log K value.