The carbanionic ring enlargement of (halomethylene)cyclobutanes to 1-halocyclopentenes has been extended to the fluoro analogues. At 180 °C, 3-hexyl-1-(fluoromethylene)cyclobutane provides better yields of rearranged product than the corresponding chloride, bromide, or iodide. At temperatures < 100 °C, the yield of ring-enlarged product follows the order I > Br > Cl, and the fluoride does not react. Experiments with labeled substrates show that, in general, the larger the halide and the higher the reaction temperature, the greater the preference for double migration over single migration as a mechanistic pathway. The trifluormethyl group is ineffective in promoting anionic rearrangement.