Fourier-transform intra-cavity laser absorption spectroscopy has been used to record high-resolution vibration-rotation overtone spectra of carbon-13 substituted acetylenes, (HC13)-C-12 CH and (HC13)-C-13 CH, in the third CH stretching overtone region between 12500 and 12730 cm(-1). The observed spectra of both species contain only parallel bands for which rovibrational spectroscopic parameters have been determined. Several anharmonic resonances have been identified and rotationally analysed using traditional vibration-rotation theory. Altogether six bands, which include v(1) + 3V(3) and 4V(3) for (HCCH)-C-12-C-13 and v(1) + 3V(3) for (HCCH)-C-13-C-13, have been observed for both species. Four of the six bands in each molecule are reported for the first time. (C) 2004 Elsevier B.V. All rights reserved.