Reaction of HCClF2 (I) or Cl2CF2 (II) with MeLi and an olefin gave 1-fluoro-1-methylcyclopropanes in fair yields. Thus, reaction of II with EtCH:CMe2 and MeLi at -78 Deg gave syn- and anti-III and IV. Depending on the reaction conditions, other cyclopropanes were obtained as well, I and II, although supposedly giving the same intermediate with MeLi, did not give the same product distribution. BuLi and PhLi gave analogous products. [on SciFinder (R)]