In the winter of 1993–1994, essays were commissioned on the topic of ambiguity and underspecification. All papers received were subjected to a thorough review process. The present volume, comprising ten self-contained papers and an introductory chapter, is the result. Natural language is known for the ambiguity of its expressions. Whereas artificial forms of communication tend to be designed in such a way that ambiguity is reduced to a minimum, natural language is ambiguous at various 'levels' of interpretation. At a low (e.g., speech recognition) level, a signal can be ambiguous between various utterances; at a higher (semantic) level, a fully recognised utterance can be used to express various different propositions; and at an even higher (pragmatic) level, a proposition may be used for various different purposes. The present volume focuses on ambiguities of the second kind, which are sometimes called semantic ambiguities, or mostly just ambiguities, when there is no likelihood of confusion.