The hydrolysis constants of trimethyl- and triethyltin(IV) ions and the stability constants for the complexation of trimethyltin(IV) with trimethylamine,N-substituted glycines (N,N-dimethylglycine andN,N,N-trimethylglycine), and aminopolycarboxylate ions (N-methyliminodiacetate, nitrilotriacetate, and ethylenediamine-N,N′-diacetate) were determined by the potentiometric method at 25 °C andI = 0.l mol dm−3((H, Na)ClO4and (H, Na)NO3). The structural parameters of Me3Sn(OH2)2, Et3Sn(OH2)2, and Me3Sn(OH2)(OH) in solution were determined by the EXAFS method. The coordination structures of trimethyltin(IV) complexes withN-substituted glycines, trimethylamine, and aminopolycarboxylate ions are discussed on the basis of the electronic interaction between the donor atom and Sn(IV).Keywords: organotin(IV), EXAFS, structure, potentiometry.