The purpose of the current research was to investigate the relation between various forms of social identity and readiness for classical and conspiracy stereotyping. The presented research project refers to the developed by Jarymowicz and her team the identity theory, which assumes the multiplicity of the social identity. Three studies were conducted during university lectures. The participants were asked to complete a set of questionnaires. 851 subjects were examined. Stereotypes were measured both explicitly and implicitly. The obtained results suggest that the social identity plays an important role in various kinds of stereotyping. It was observed that the categorical form of social identity is the most, whereas the attributional form of social identity is the least conductive for all kinds of stereotyping.