A series of optically active silatrane derivatives, [Si{N(CHRCH(2)O)(CH2CH2O)(2)}X] (R = Me, i-Pr; X = Ph, OMe) has been synthesized by the reaction of optically active triethanolamine derivatives with XSi(OMe)(3), and characterized by H-1 NMR, C-13 NMR, Si-29 NMR, and mass spectroscopy, and the structures of six compounds have been determined by X-ray analysis. Molecular mechanics methods have also been employed to obtain the energy-minimized structures. The Si-29 NMR chemical shifts and the lengths of Si-N determined by X-ray analysis are sensitive to the bulkiness of the substituent (R). The Si-X bond lengths (X : trans position to nitrogen) do not appreciably differ from one another. -The MM2 calculations indicated that the substituent exists in the equatorial position, and the results are in agreement with those of X-ray analysis and H-1 NMR spectroscopy. Crystallographic data : [R = H; X = OMe], C7H15NO4Si, orthorhombic, Pna2(1), a = 13.407(1) Angstrom, b = 8.761(2) Angstrom, c = 8.191(1) Angstrom, Z = 4; [R = Me; X = OMe], C8H17NO4Si, orthorhombic, P2(1)2(1)2(1), a = 10.110(3) Angstrom, b = 11.083(2) Angstrom, c = 9.474(2) Angstrom, Z = 4 [R = i-Pr; X = OMe], C10H21NO4Si, monoclinic, P2(1), a = 8.481(1) Angstrom, b = 7.805(1) Angstrom, c = 10.218(2) Angstrom, beta = 111.31(1)degrees, Z = 2; [R = Me; X = Ph], C13H19NO3Si, orthorhombic, P2(1)2(1)2(1), a = 8.813(1) Angstrom, b = 11.137(2) Angstrom, c = 13.757(1) Angstrom, Z = 4; [R = i-Pr; X = Ph], C15H23NO3Si, orthorhombic, P2(1)2(1)2(1), a = 8.365(1) Angstrom, b = 13.538(2) Angstrom, c = 13.841(2) Angstrom, Z = 4.