Lexical acquisition is the automatic production or augmentation of a lexicon for a natural language processing system. The lexical information acquired includes the forms, meanings, collocations, and associated statistics of the lexical entries (lexemes). This process is vital to produce systems that can handle real life data. This article discusses current approaches for acquiring lexical information from available resources, such as corpora and machine readable dictionaries and thesauruses. It describes the different types of lexical information acquired and the techniques that have been used in the process.