  We investigate Lie symmetries of general Yang-Mills equations. For this
purpose, we first write down the second prolongation of the symmetry generating
vector fields, and compute its action on the Yang-Mills equations. Determining
equations are then obtained, and solved completely. Provided that Yang-Mills
equations are locally solvable, this allows for a complete classification of
their Lie symmetries. Symmetries of Yang-Mills equations in the Lorentz gauge
are also investigated.
