Six new herbicidal protic ionic liqs. were synthesized by quarternization of RNMe2 (I, R = (CH2)(2)OH, (CH2)(3)OH) with 2-R-3-CIC6H3OCH2COOH (II, R = Me or Cl) or 2-MeO-3,4-Cl2C6H2COOH (III), identified by elementary anal., and H-1- and C-13-NMR spectroscopies, and studied for thermal stability research and biol. activity against cornflower (Centaurea cyanus) and white mustard (Sinapis alba). The new ionic liqs. showed higher herbicidal activity than corm herbicides except for the salts of I with II (R = Cl) and with III.