Methylated and hydroxylpropylated cyclodextrins (CDs) are highly efficient mass transfer promoters in biphasic aqueous organometallic processes. The surface tension measurements demonstrated that these CDs adsorb at air-water interface and allowed to determine surface excess of CD by using Gibbs adsorption equation. Interestingly, a good correlation between surface excess and catalytic activity was obtained in the case of hydroformylation and Tsuji-Trost reactions. These results point out the importance of CD adsorption at the interface in biphasic aqueous organometallic processes. (c) 2006 Elsevier Inc. All rights reserved.