A new method of stabilizing acid deteriorated vegetable tanned leather is proposed by retannage with aluminum alkoxides. The aluminum alkoxide is applied in a non-polar organic solvent, the aluminum reacting with vegetable tannins in the leather to raise its pH, shrinkage temperature and resistance to further atmospheric deterioration. Two aluminum alkoxides soluble in a non-polar solvent were found to be capable of retanning vegetable tanned leather in situ. When new vegetable tanned leather retanned with these compounds was aged in a deterioration chamber the rate of deterioration was substantially reduced compared with the same leather without retannage. When aged acid leathers were treated by surface application of the retanning compounds the shrinkage temperature was raised 20-30 C and the pH was raised above 3. Retannage with the aluminum alkoxides produced minimal color change but there was a tendency to stiffen the leather possibly as a result of chemical bonding between aluminum and the leather. Stiffening can be substantially reduced by the application of a suitable lubricant after retannage. Retannage with aluminum alkoxides can be considered an effective stabilizing treatment for acid deteriorated leather as well as a new vegetable tanned leather used for backing or repair work.