A comprehensive analysis of English "as" clauses in terms of distribution and interpretation is offered. It is hypothesized that "as" clauses provide a supplementary explanation to the head noun (adnominal "as" clauses) and provide the propositional content of the main clauses (sentential "as" clauses.) "As" clauses, whether they seem to function as adnominal or sentential, should be regarded as adverbial clauses. (Contains 19 references.) (JP)