Lithium tetramethylcuprate(III), Me₄CuLi, the Cu^III analog of the Gilman reagent, has been prepared in high yield from halo-Gilman reagents Me₂CuLi·LiX (X = Cl, Br, I) and 2,3-dichloropropene and found to have surprising thermal stability. The cyano-Gilman reagent (X = CN) follows a different pathway.