Polarized optical absorption and emission measurements are used to locate and assign 91 crystal-field energy levels split out of the 4f(9) electronic configuration of Dy3+ in hexagonal Na-3[Yb1-xDyx(dpa)(3)]. NaClO4 . 10H(2)O (x = 0.05, 0.2, 1; dpa = dipicolinate dianion = 2,6-pyridinedicarboxylate). The absorption measurements span the 300-1800 nm wavelength range, and the emission measurements span the 470-775 nm wavelength range. The combined absorption and emission measurements provide access to the energy-level structures of 35 4f(9) [SL]J multiplet manifolds of Dy3+, which include all multiplet manifolds with baricenter energies < 33 000 cm(-1) above ground. The site symmetry of the Dy3+ ions in hexagonal Na-3[Yb1-xDyx(dpa)(3)]. NaClO4 . 10H(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 187 crystal-field levels predicted for the 35 multiplet manifolds examined in this study, 91 are both located and assigned (with respect to crystal-field symmetry type, E’ or E ", and principal [SL]J multiplet parentage). The 91 assigned levels are analyzed in terms of a model Hamiltonian that includes consideration of both isotropic and non-isotropic 4f-electron/crystal-field interactions. A parametrized form of this Hamiltonian is used to perform parametric fits of calculated-to-experimental energy-level data, and the results obtained from these fits show an rms deviation of 6.3 cm(-1) between calculated and observed energies, The interaction parameters evaluated from these energy-level data fits are compared to those for Dy3+ in other systems, with particular attention given to Dy(oda)(3)(3-) in Na-3[Dy(oda)(3)]. 2NaClO(4) . 6H(2)O (where oda = oxydiacetate). The crystal-field energy-level structures of Dy(oda)(3)(3-) and Dy(dpa)(3)(3-) show significant differences, and these differences are discussed in terms of the ligand moieties that are present in the respective complexes. Among the more than 150 spectral features observed and assigned in the unpolarized axial absorption spectra of Na-3[Dy(dpa)(3)]. NaClO4 . 10H(2)O, 46 are sufficiently well-resolved to permit quantitative determinations of transition line strengths, and these line strengths are reported and discussed.