A temperature study of the partially deuterated monomeric methanol species CH 2DOH(D) and CHD 2OH(D) isolated in Ar, Kr, Xe, and N 2 matrices is reported. The rotamers of a given species were found to interconvert upon temperature cycling owing to slightly different stability. Experimental confirmation is provided for the differences in zero point energy of rotamers obtained earlier from spectroscopic data. The importance of sample-matrix interactions is demonstrated by the observation that the interconversion of rotamers was completely reversible if the matrices were in an amorphous state but partially or totally inhibited as the matrices grew more crystalline. The two states were observed for all four matrices, depending on deposition conditions and temperature cycling rates.