Ba(6-x)Ln(x)Nb(10)O(30) compounds, Ln = La, Ce and Nd, with a tetragonal tungsten bronze-type structure have been synthesized and were characterized by X-ray powder diffraction and EDS analysis. The homogeneity regions of the obtained compounds were found to be 0 less than or equal to x less than or equal to 2 for La, and 0 less than or equal to x less than or equal to 1.5 for Ce and Nd. The crystal structures of Ba5LaNb10O30 and Ba4La2Nb10O30 were refined using X-ray powder diffraction data. Refinement indicated the presence of vacancies in the Ba/La positions. This observation was supported by oxidation studies of the La-substituted compounds. The temperature dependence of the normalized resistivity of the compounds showed a nonmetallic behavior. The increase in the R/R(273) ratio with decreasing temperature is less distinct for the phases with the higher concentration of rare-earth cation.