Despite the fundamental importance of multicultural group work activities in the curriculum, previous literature has shown that home and international students do not spontaneously mix and would rather be involved in monocultural work groups. One of the major causes for this lies in the home students' belief that assessed multicultural group work has a detrimental effect on their individual average mark. Using data from a large cohort enrolled on a first-year business studies programme of a UK university, this study employs regression analysis to empirically investigate the extent to which this belief is supported by the data. The results suggest that the performance of culturally mixed groups is neither a function of the individual ability of the least able group member, nor of the average ability of the members of the group. Instead, in this context, the group work mark is more likely to reflect the ability of the most able group member. The data also indicate that assessed multicultural group work has, on average, a positive rather than negative effect on the individual average mark of all students, evidence consistent with the synergistic effects expected to emerge in multicultural groups.