2-Methylpropionic acid was with 2-methylpropanol (I) or 3-hydroxy-2,2,4-trimethylpentyl 2-methylpropionate (II) and the resulting ester product was distd. Sulfuric acid, p-toluenesulfonic acid, or Dowex 50Wx8 was used as catalyst. With I and II, 2-methylpropyl 2-mtrhylpropionate and 2,2,4-trimethylpentyl di(2-methylpropionate) (III) were the major products, resp. With H2SO4 as catalyst, 0.5 mole%/mole, an excess of the alc. over the aciid, 1.72, was advantageous. The heterogeneous catalyst was less active. Over strongly acid catalysts, III hydrolyzed to yield I and II.