The preparation is described of 4,4′-bipyridylium salts bearing aryl substituents α to one of the heterocyclic nitrogen atoms. Evidence from u.v. and n.m.r. spectra suggests that in the quaternary salts the aryl groups are prevented from assuming co-planarity with the bipyridyl nucleus by the steric effect of the N-methyl group. The compounds were inactive in herbicide tests.