In view of its exploratory nature, Chomsky's 'minimalist' model has undergone multiple changes, triggering in response numerous proposals that are consistent with the tendencies that it follows or anticipates, and numerous proposals that offer alternatives to it. A good illustration of the variety of 'parallel' proposals is provided in the present volume. The articles derive from papers read at the "Challenges of Minimalism" session of the Open Linguistics Forum, held in Ottawa, in March 1997. This OLF meeting started as a graduate student initiative, but because of the topic chosen, attracted a wide and international audience. The twenty contributions are grouped in five sections: I. Syntactic Structure, Relations, Operations; II. Syntactic Movement: Cyclicity, Optionality, (Non)overtness; III.Case, Topic, Focus, Interrogativity; IV. Ellipsis, Reconstruction and Related Phenomena; V. DPs: Features and Syntactic Relations.