This study used meta-analysis: (a) to quantify the relationship between descriptive norms and intentions, and (b) to determine the increment in variance attributable to descriptive norms after variables from the theory of planned behaviour (TPB; Ajzen, 1991) had been controlled. Literature searches revealed twenty-one hypotheses based on a total sample of N = 8097 that could be included in the review. Overall, there was a medium to strong sample-weighted average correlation between descriptive norms and intentions (r+ = .44). Regression analysis showed that descriptive norms increased the variance explained in intention by 5 percent after attitude, subjective norm, and perceived behavioural control had been taken into account. Moderator analyses indicated that younger samples and health risk behaviours were both associated with stronger correlations between descriptive norms and intentions. Implications of the findings for the conceptualization of social influences in the TPB are discussed.T he theory of planned behaviour (TPB; Ajzen, 1991) is perhaps the most influen tial theory for the prediction of social and health behaviours. This model is an extension of the theory of reasoned action (TRA; Ajzen & Fishbein, 1980) and incorporates both social influences and personal factors as predictors. Social influences are conceptualized in terms of the pressure that people perceive from important others to perform, or not to perform, a behaviour (subjective norm). Subjective norm is determined by beliefs about the extent to which important others want them to perform a behaviour (normative beliefs, e.g., "My friends think that I should engage in a binge drinking session") multiplied by one's motivation to comply with those people's views (e.g., "I generally want to do what my friends think I should do"). Subjective norms are proposed to influence behaviour through their impact upon intentions, (e.g., "I intend to engage in a binge drinking session"). Intentions summarize a person's motivation to act in a particular manner and indicate how hard the person is willing to try and how much time and effort he or she is willing to devote in order to perform a behaviour. Also important in the prediction of intentions are people's positive or negative evaluations of their performing a behaviour (attitudes, e.g., "For me, engaging in a binge drinking session would be wise/foolish") and the degree of control that they believe they have over performing the behaviour (perceived behavioural control, e.g., "Engaging in a binge drinking session is entirely under/outside my control"). Like subjective norms, attitudes and perceived behavioural control are determined by cer-