  We present an analysis of a high resolution (R = 40000) infrared spectrum of
the RS Oph secondary around the first overtone CO bands, obtained in 2008 May
on the Gemini South 8 m. The 12CO and 13CO bands are well-resolved, and we
compute synthetic spectra to determine the 12C/13C ratio. We find 12C/13C = 16
+/- 3, consistent with the interpretation of the secondary as red giant which
has evolved beyond the first drege-up phase of evolution.
