This paper concerns both anaphora resolution and prepositional phrase (PP) attachment that are the most frequent ambiguities in natural language processing. Several methods have been proposed to deal with each phenomenon separately, however none of proposed systems has considered the way of dealing both phenomena. We tackle this issue, proposing an algorithm to co-ordinate the treatment of these two problems efficiently, i.e., the aim is also to exploit at each step all the results that each component can provide.