AbstractMethyl 2‐lithioisobutyrate (LIMIB) is shown to form 3:1, 2:2 and 1:3 complexes with lithiumtert‐butoxide (LTB) in THF, depending on their molar ratio and storage time. The rate of formation of the complexes varies inversely as their stability: the 3:1 (LIMIB:LTB) complex is formed immediately but is not very stable; the full formation of the 1:3 complex takes about 20 h at −15°C but the product can be kept for several hours at room temperature without marked change.1H,13C,6Li and7Li NMR and MNDO results suggest that the core of any kind of the complex is formed by a cubic (Li‐0)4structure with each of the four Li atoms bound to three equivalent oxygens. The structure of the complexes with lesstert‐butoxide is less tightly packed. The complexes do not exhibit intermolecular exchange of Li atoms; their intramolecular exchange was not found but cannot be excluded. Preliminary results are presented for living MMA oligomers prepared by initiation with the LIMIB‐LTB system. The structure of these oligomers is not significantly affected by the equilibrium state of the initiation system. The living centre is found to be coordinated both to LTB and to the penultimate ester group. Although improved in stability by LTB coordination, the living oligomers exhibit marked self‐termination in THF