Looking at evolution as the process of HOW God created the world does not pose a problem for the Catholic. However, because some aspects of "evolution" can impact the faith of the believer, the Church does offer guidelines for what must be believed and what is left up to the individual's judement. Before considering those guidelines, let's be clear about the difference between "evolution" and "evolutionism." Evolution is a scientific THEORY that says more complex forms of life developed from less complex life forms, over extremely long periods of time (perhaps a couple of billion years). As a scientific theory, it is to accepted or rejected based on the evidence. (My answer continues in the comments)
Catholics believe that the in the theory of evolution though they state that human beings are special creation. They argue this fact with the existence of God who they say is responsible for the existence of humans. Visit http://en.wikipedia.org/wiki/Catholic_Church_and_evolution for more information.
That, human are "modified DUST" - created by the cruel whims of a tyrannical being called "god".
They do not regard god as a vague "spirit," nor as an "essence" without body or parts, but as a being, a person, an infinite man, a king, the monarch of the universe, who had created human for love and yet had the vague vanity to award garments of glory for believers and robes of flame for the heretic and infidel.