Optical absorption and emission measurements are used to locate and assign 152 crystal-field energy levels split out of the 4f(9) electronic configuration of Dy3+ in Na-3[Dy(oda)(3)]. 2NaClO(4) . 6H(2)O (where oda denotes an oxydiacetate ligand). The absorption measurements span the 230-1800 nm wavelength range, and they encompass all optical transitions that may occur between the H-6(15/2) ground multiplet and 63 different excited multiplet manifolds of the 4f(9)(Dy3+) electronic configuration. The emission measurements span the 470-900 nm wavelength range, and they encompass all transitions that originate within the F-4(3)(9/2) excited multiplet manifold (centered at ca. 21 100 cm(-1) above ground) and terminate on levels split out of the H-6(J) (J = 15/2, 13/2, 11/2, 9/2, and 7/2) and F-6(J) (J = 11/2, 9/2) multiplet manifolds of 4f(9)(Dy3+). The combined absorption and emission measurements provide access to the energy-level structures of 65 4f(9)[SL]J multiplet manifolds of Dy3+ (all multiplet manifolds with baricenter energies <43 000 cm(-1) above ground). The site symmetry of Dy3+ ions in Na-3[Dy(oda)(3)]. 2NaClO(4) . 6H(2)O is D-3, and all crystal-field levels split out of the 4f(9)(Dy3+) electronic configuration are Kramers doublets with either E’ or E " symmetry in the D-3 double-rotation group. Among the 348 crystal-field levels predicted for the 65 multiplet manifolds examined in this study, 152 are both located and assigned (with respect to crystal-field symmetry type, E’ or E ", and principal [SL]J multiplet : parentage). Symmetry assignments are based on results obtained from both linearly and circularly polarized absorption and emission measurements. : parentage). Symmetry assignments are based on results obtained from both linearly and circularly polarized absorption and emission measurements.