Mobile learning differs from learning in the classroom or on a desktop computer in its support for education across contexts and life transitions. This poses substantial problems for evaluation, if the context is not fixed and if the activity can span formal and informal settings. There may be no fixed point to locate an observer, the learning may spread across locations and times, there may be no prescribed curriculum or lesson plan, the learning activity may involve a variety of personal, institutional and public technologies, it may be interleaved with other activities, and there may be ethical issues concerned with monitoring activity outside the classroom. The chapter indicates issues related to evaluation for usability, effectiveness and satisfaction and illustrates these with case studies of evaluation for three major mobile learning projects. The Mobile Learning Organiser project used diary and interview methods to investigate students’ appropriation of mobile technology over a year. The MyArtSpace project developed a multi-level analysis of a service to support learning on school museum visits. The PI project has employed critical incident analysis to reveal breakthroughs and breakdowns in the use of mobile technology for inquiry science learning. It is also addressing the particular ethical problems of collecting data in the home.