Me groups adjacent to an olefinic double bond were metalated by KOCMe3 and BuLi without cis-trans isomerization. Thus, (E)-MeCH:-CHMe was metalated to give (E)-MeCH:CHCH2K (I) which reacted with ethylene oxide to give 41% (E)-MeCH:CH(CH2)3OH. If I was allowed to equilibrate, the Z-isomer predominated (>99:1). Longer-chain olefins were metalated more slowly, with side reactions taking place. Thus, metalation of BuCH:CMe2 with EtCHMeBu and KOCMe3, followed by reaction with MeI gave 45% (Z)-BuCH:CMeEt, 9% BuCHMeCMe:CH2, and 19% Me(CH2)4CEt:CH2. [on SciFinder (R)]