Activity coefficient of triethanolamine (TEA) in major seawater salts (NaCl, KCl, CaCl, and MgCl2) has been determinated using the distribution method. It increases slowly in KCl, remains almost constant in NaCl and decreases in the other salts. Pitzer model has been used to fit the experimental data and the corresponding interaction parameters have been determinated. (c) 2005 Elsevier B.V. All rights reserved.