Abstract. The behaviorist view of learning that informs much of traditional schooling is not likely to invite students and teachers to see errors in a positive light. This is particularly true for mathematics. Our goal is to change this situation by including erroneous examples and other error-related learning opportunities in ActiveMath. This paper investigates the systematic design of erroneous examples. For this, it analyzes the potential benefits that erroneous examples can have and distinguishes different presentation patterns. This analysis together with first experiences from school and from a university course with ActiveMath informs further research on effects, adaptive choice and presentation of erroneous examples in ActiveMath.