9-Methylhydrindan-1-one was obtained as a mixture (80% trans, 20% cis) in four steps from 10-methyl-Δ1,9-octal-2-one. In the presence of alkali it epimerized to cis-9-methylhydrindan-1-one containing less than 1% of the trans isomer. Oxidation of this cis ketone with peroxytrifluoroacetic acid gave cis-1-oxa-10-methyldecal-2-one.