The terbium myristate has been investigated by IR, X-ray diffraction and thermogravimetric anal-ysis (TGA). The IR result reveals that fatty acids exist as dimer through hydrogen bonding and terbium myristate possess partial ionic character. The X-ray diffraction suggests that molecular axes are somewhat inclined to the basal plane. The metal cation fit into spaces between oxygen atoms of the ionised carboxyl group without giving a large strain of the bond. The thermal decomposition reaction is found kinetically of zero order and value of ener-gy of activation is in the region of 3.84 to 8.55 K cal mol-1.