We have synthesized single crystals of the misfit layer cobaltate [Sr,TIO3][CoO2](1.77) and determined its crystal structure by the means of X-ray single-crystal diffraction (XRSD) and transmission electron microscopy. The synthesis took place by spontaneous crystallization from an oxide melt at high gaseous pressure. The structure is described by two monoclinic subsystems, which share the unit cell parameters, a = 4.933(5),angstrom, c = 11.470(12) angstrom, and beta = 98.00(10)degrees, but are incommensurate in the direction of b-axes: b, = 5.009(8) A and b(2) = 2.830(8) angstrom, where b, is for the subsystem [Sr2TIO3] and b, for [CoO2]. The layer sequence in the structure consists of Cdl(2)-type structured (CoO2,)(infinity) and three puckered rock-salt (RS) layers, two of which are (SrO)(infinity) and one (TIO)(infinity). The solved structure confirms that the thermoelectric compounds [Ca2COO3][COO2](1.62) (Co-121) and [Sr2TlO3][CoO2](1.77) (TI-121) are isostructural. (c) 2007 Elsevier B.V. All rights reserved.