Crystals of theN,N-dimethylethanolaminogallane dimer1aare monoclinic,a = 8.540(1),b = 7.0433(7),c = 12.227(6) Å, β = 92.94(3)°,Z = 2, space groupP21/cand crystals of theN,N-dimethylethanolaminogallium dimethyl dimer1bare orthorhombic,a = 15.608(3),b = 11.655(2),c = 10.266(2) Å,Z = 4, space groupPccn. Both structures were determined by Patterson and Fourier syntheses and were refined by full-matrix least-squares procedures to finalRvalues of 0.039 and 0.053 for 1062 and 1155 reflections with1 ≥ 3σ(I) respectively. Both structures feature well-separated centrosymmetric dimeric units occurring via the formation of four-membered Ga2O2rings. The five-coordinate gallium atoms have distorted trigonal bipyramidal geometry. Steric interactions between methyl groups in1bare believed responsible for the lengthening of the axial Ga—N distance from 2.279(3) in1ato 2.471(4) Å in1b. Other bond distances are: for1a; Ga—O (axial), 2.053(3), Ga—O, 1.911(3), Ga—H, 1.50(7) and 1.73(5), O—C, 1.369(5), N—C, 1.466 – 1.485(6), C—C, 1.512(7), and mean C—H, 1.05; for1b; Ga—O (axial), 2.078(3), Ga—O, 1.913(3), Ga—C, 1.936(6) and 1.948(7), O—C, 1.382(7), N—C, 1.452–1.482(7−8), C—C, 1.516(9), and mean C—H, 1.01 Å.