We have carried out a qualitative study of factors that influence the evaluation of telehealth. The study concerned six telehealth projects that are being tracked over two years. In the first 12 months of the study we carried out semistructured interviews and made observations of the participants in the projects. Each case study involved 5-15 subjects, many of whom were interviewed several times. The results indicate that important issues affecting telehealth evaluation include developing and maintaining the technology, reorganization of clinical and administrative duties, professional dynamics, and the difficulty of integrating service provision and evaluation. The findings suggest that the evaluation of telehealth interventions is highly complex, and that this complexity is often underestimated in the design and conduct of evaluation studies.