Black individuals are usually reluctant to co-operate with the police (Smith, 1983a). We propose that a history of unpleasant interactions with the police generates hostile attitudes towards the institution (Jefferson & Walker, 1993). Using a sample of 56 black and 64 white participants, we examined whether quality of contact predicts black people's attitudes and subjective norms concerning co-operating with the police. Our findings indicated that the Contact Hypothesis (Pettigrew, 1998) and Theory of Planned Behaviour (Ajzen, 1991) jointly provide some insight into the disinclination of black individuals to co-operate with the police. We found that the relationship between race and attitudes or subjective norms concerning co-operation with police investigations was mediated by quality of previous contact with the police. In turn, the relationship between quality of contact and willingness to co-operate with police investigations was mediated by both attitudes and subjective norms. Theoretical and practical implications are discussed.