There is a common opinion that mathematics is difficult for persons with Down syndrome, because of a weakness in numeracy and in abstract thinking. Since 1996, some single case studies have suggested that new opportunities in mathematics are possible for these students: some of them learned algebra and also learned to use equations in problem-solving. Here an educational study with 15 teenagers with Down syndrome is presented: fractions, percentages, first-degree equations and problem-solving with equations were taught and learning was monitored. The students' performances during the course and in a final test were compared: the students seemed to have learned the new programme and to remember it one month later. They seemed to perform better with equations and problem-solving with equations than with other more conventional topics. There were no significant differences in the performance of different gender groups. (Contains 1 table, 5 figures and 1 note.)