The regioselective metalation of s-collidine yielding two anions, trapped by PhCN, was found to be essentially determined by the solvent and the size of the cation: twelve solvents and three cations (Li+, Na+, K+) were examined. The effect of various bases (alkali metals, phenyllithium, amides, “complex bases”, amines) and of some metallic cations (Li+, Ag+, Pd2+) was studied. The solvent basicity