Personal pronouns represent important social categories; they are among the most common words in communication and are therefore highly interesting in studying psychological perspectives and relations. The aim of this thesis was to investigate whether pronouns are used in semantic contexts in a way that reflect psychological biases. Specifically, I have tested whether self-, group-serving- and gender biases occur when pronouns are used in natural language. To study this, I developed a structure for pronouns in social categorization where the pronouns are categorized in a self-inclusive/exclusive, an individual/collective, and a gender dimension. New methods for examining pronouns usage in language were developed in the thesis, for use in experiments and in computerized studies of large data corpora of media news. The results of this thesis showed that self-inclusive pronouns (I, We) consistently were used in more positive contexts than self-exclusive pronouns (He, She, They) by participants who generated messages in the lab (Study I), and by journalists in written media news (Study II). Study I revealed that the evaluative context surrounding I and We varied according to the specific communicative situation. When individuals generated messages individually, more positive contexts were selected for I than We. However in a collaborative setting, We occurred in contexts of similar valence as I. An intergroup setting magnified the differences between self-inclusive and self-exclusive pronouns (e.g., between We and They and between I and He/She). In an analysis of 400 000 news media messages, We occurred in more positive context than I (Study II). In Study III, the contexts of He and She in these media news were examined. The results showed that He occurred nine times more often, and in more positive contexts than She. Moreover, words associated with She included more labels denoting gender, and were more uniform than words associated with He. In sum, this thesis shows that studying the use of pronouns is a fruitful way to investigate social psychology phenomena. The thesis contributes to the understanding of how pronoun use convey knowledge about social cognition, attitudes, gender stereotypes, as well as interpersonal and intergroup relations.