This thesis deals with four indefinite pronouns: somebody, someone, anybody, anyone. My aim is to investigate the difference between these semantically similar lexical items. The study is conducted using the British National Corpus, a 100 million words corpus representing British English from the late 20th century. This corpus-based study includes certain fields of investigation:- distribution in the BNC material: frequency per million words;- distribution in the written and spoken material: frequency per million words in text domains;- gender of pronouns: agreement of co-referent pronouns with their antecedents (third person plural, third person singular masculine, third person singular feminine, third person singular masculine/feminine);- modification by adjectives: semantic types of adjectival modifiers;- polarity of sentences: declarative, interrogative, exclamatory and imperative sentences. The use of body and one pronouns is complex. The BNC material shows that indefinite pronouns under study in fact differentiate depending on the domain of usage, the use of co-referents and sentence types.