We present the first high-resolution stimulated Raman study of osmium tetroxide (OsO4). Lines from the ν1 totally symmetric stretching fundamental have been assigned. These data together with the infrared assignments of the ν3 band previously recorded (M. Louviot et al., J. Quant. Spectrosc. Radiat. Transfer, 2012, 113, 119–127) allowed a refinement of the analysis of the ν1/ν3 stretching dyad. We found that the ν1 band has an unusual positive isotopic shift of approximately 0.32 cm− 1/amu, which gives further evidence that the stretching dyad should be perturbed by a complex nearby bending band polyad. This work is part of a global effort to analyze all fundamental bands of OsO4 to obtain a more precise experimental value of the ground state bond length for this heavy metal-containing molecule. The result could serve as a benchmark for high-level quantum chemistry calculations. Copyright © 2012 John Wiley & Sons, Ltd.