This chapter looks at methods and criteria for strengthening the trustworthiness of qualitative research findings. The key is internal validity, which can be strengthened through data triangulation, ongoing researcher reflectivity, data saturation and member checks. Internal reliability, the agreement of another researcher, also contributes to internal validity. External reliability or naturalistic generalization involves making theoretical interpretations of local findings in order to apply understandings to other settings. Insider and outsider research positions, and the strengths and challenges of each, are examined.