Phenol-formaldehyde resins are important adhesives used by the forest products industry. The phenolic compounds in these resins are derived primarily from petrochemical sources. Alternate sources of phenolic compounds include tannins, lignins, biomass pyrolysis products, and coal gasification products. Because of variations in their chemical structures, the reactivities of these phenolic compounds with formaldehyde vary in quite subtle ways. Previously, it was demonstrated teat the reactivity of a number of phenols with formaldehyde in nonaqueous conditions could be correlated with charges calculated for reactive sites on the aromatic ring (Conner, A. H. J Appl Polym Sci 2000, 78, 355-363). We studied the reactivity of a larger number of phenolic compounds with formaldehyde in an aqueous solution using sodium hydroxide as the catalyst. Reaction rates were determined from measurements of the concentrations of the phenolic compounds and formaldehyde as functions of time. The reaction rate constants varied over a wide range (approximately 10(-2) to 10(4) L mol(-1) h(-1)). An estimate of the reactivity per reactive site on the phenolic ring was determined by dividing the rate by the number of reactive sites. Atomic charges for each phenolic compound were calculated by ab initio methods at the RHF/6-31+ G level of theory using the CHelpG method. The charge per reactive site was estimated by summing the charges at all the reactive sites on the phenolic ring and dividing by the number of reactive sites. A strong correlation was observed between the reactivity per reactive site and the average charge per reactive site.