A systematic algorithm for building integrating factors of the form mu(x,y')
or mu(y,y') for non-linear second order ODEs is presented. When such an
integrating factor exists, the algorithm determines it without solving any
differential equations. Examples of ODEs not having point symmetries are shown
to be solvable using this algorithm. The scheme was implemented in Maple, in
the framework of the ODEtools package and its ODE-solver. A comparison between
this implementation and other computer algebra ODE-solvers in tackling
non-linear examples from Kamke's book is shown.