The infrared spectrum of dimeric methyl iodide produced in a supersonic jet has been re-measured in the C-H stretching region by cavity ring-down spectroscopy with higher resolution, 0.03 cm(-1). Two absorption bands of the dimer, which could not be observed in our previous study [F. Ito, T. Nakanaga, Y. Futami, M. Nakata, Chem. Phys. 286 (2003) 337] have been identified. Analyses including peak decomposition and contour simulation have led to the assignment of the two bands to the head-to-head and head-to-tail isomers of (CH3I)(2). (c) 2005 Elsevier B.V. All rights reserved.