OBJECTIVES: Generally, in most countries around the world, local medical students outperform, in an academic sense, international students. In an endeavour to understand if this effect is caused by language proficiency skills, we investigated academic differences between local and international MBBS students categorised by native language families. METHODS: Data were available and obtained for medical students in their first and second years of study in 2002, 2003, 2005 and 2006. Information on social demographics, personal history and language(s) spoken at home was collected, as well as academic assessment results for each student. Statistical analysis was carried out with a dataset pertaining to a total of 872 students. RESULTS: Local students performed better than international students in first- (p <0.001) as well as second-year (p <0.001) assessments. In addition, there was a main interaction effect between language family and origin in the first year (p <0.05). For international students only, there was a main effect for language in the second year (p <0.05), with students from Sino-Tibetan language family backgrounds obtaining higher mean scores than students from English or Indo-European language family backgrounds. CONCLUSIONS: Our results confirmed that, overall, local students perform better academically than international students. However, given that language family differences exist, this may reflect acculturation rather than simply English language skills.