We present qualitative research findings about how perceptions of criminal prosecutions for the transmission of HIV interact with the provision of high-quality HIV health and social care in England and Wales. Seven focus groups were undertaken with a total of 75 diverse professionals working in clinical and community-based services for people with HIV. Participants' understanding of the law in this area was varied, with many knowing the basic requirements for a prosecution, yet lacking confidence in the best way to communicate key details with those using their service. Prosecutions for HIV transmission have influenced, and in some instances, disrupted the provision of HIV services, creating ambivalence and concern among many providers about their new role as providers of legal information. The way that participants approached the topic with service users was influenced by their personal views on individual and shared responsibility for health, their concerns about professional liability and their degree of trust in non-coercive health promotion approaches to managing public health. These findings reveal an underlying ambivalence among many providers about how they regard the interface between criminal law, coercion and public health. It is also apparent that in most HIV service environments, meaningful exploration of practical ethical issues is relatively rare. The data presented here will additionally be of use to managers and providers of HIV services in order that they can provide consistent and confident support and advice to people with HIV.