We present a study investigating the role of social identity processes in the explanation of intergroup differences. By transposing the fundamental attribution error hypothesis (Pettigrew, 1979), we predict that the explanation for differences favoring the out-group will be preferentially attributed to "external" factors (socio-structural factors or the action of a deviant sub-group). When differences favour the in-group, internal explanations (emphasizing cultural differences or differences in personality traits) are more likely to be selected. Moreover, if these differences are driven by identity protection, they should be highest among high identifiers. The study, which was conducted among Dutch-Speaking (N = 53) and French Speaking (N = 50) Belgian students, involved the explanation of four differences between the two linguistic groups. The data support the hypotheses in the case of two of these differences, French speakers being more likely to attribute differences favoring the in-group to internal causes than Dutch speakers, especially if they are strongly identified with their linguistic group. Results with respect to the two other differences are discussed within the framework of social identity theory. ; SCOPUS: ar.j ; info:eu-repo/semantics/published