Understanding abstract concepts and ideas in mathematics, if instruction takes place in the first language of the student, is difficult. Yet worldwide students often have to master mathematics via a second or third language. The majority of students in South Africa--a country with eleven official languages--has to face this difficulty. In a quantitative study of first year calculus students, we investigated two groups of students. For one group tuition took place in their home language; for the second group, tuition was in English, a second or even a third language. Performance data on their secondary mathematics and first year tertiary calculus were analysed. The study showed that there was no significant difference between the adjusted means of the entire group of first language learners and the entire group of second language learners. Neither was there any statistically significant difference between the performances of the two groups of second language learners (based on the adjusted means). Yet, there did seem to be a significant difference between the achievement of Afrikaans students attending Afrikaans lectures and Afrikaans students attending English lectures. (Contains 9 tables.)