Pyridine-2,6-dicarboxylic acid (pdcH(2)) reacts with LaCl(3)center dot 7H(2)O under hydrothermal conditions followed by evaporation at room temperature to give a metal-organic framework structure of the empirical formula, [La(pdc)(H2O)(4)]center dot Cl (1), in the form of infinitely long bunched nanotubes. The chloride ions and water molecules occupy the tubular as well as the inter-tubular spaces. When La(NO3)(3)center dot 7H(2)O is used in place of LaCl(3)center dot 6H(2)O, a similar structure is formed with the empirical formula, [La(pdc)(H2O)(4)]-NO3 (2), where water molecules and the nitrate anions occupy the voids as in the case of 1. When an aqueous solution of AgNO3 is added to an aqueous solution of 1, the Cl- ions are replaced completely by NO3- ions to form 2; thus, the tubular structure is conserved. However, when AgBF4 is used in place of AgNO3, the tubular structure breaks down, and a new 3-D MOF structure, [La(pdc)(pdcH)(H2O)(2)]center dot 4H(2)O (3), is formed where the cavities are occupied by hexameric and dimeric water clusters. Structure 3 is also formed as the sole product when La(OAC)(3)center dot xH(2)O is treated with pyridine-2,6-dicarboxylic acid following the method adopted for 1 and 2. Formation of the tubular structure depends on the molar ratio of the ligand and the metal. When higher than 1 equiv of the metal is taken, a linear coordination polymer, [La-2(pdC)(3)(H2O)(6)]center dot 2H(2)O (4), is formed, This study provides the first nanotubular structure of a pure lanthanide metal.