While certainly not a new phenomenon, the exploitation of children and vulnerable adults in 'county lines' drug distribution and sales now attracts considerable attention and concern. In this study, we explored professionals' perspectives on understandings of and responses to this issue in the West Midlands, UK. We conducted in-depth interviews with 11 participants from policing, prosecution, government and the third sector. Participants typically saw county lines-related exploitation as insufficiently understood, especially where individuals are both victimised and commit offences are concerned. They also characterised responses as hampered by factors such as variable use of legislation, inconsistent intelligence sharing and insufficient resourcesparticularly to support vulnerable people. More robust multiagency collaboration could help address these issues, although it also involves challenges. Our exploratory study focuses on criminal justice responses to county lines-related exploitation in particular, a relatively narrow set of professionals and one specific geographical location, meaning findings must not be overextended. Nevertheless, it provides novel insights into a complex, important and understudied phenomenon. We situate the work against the broader literature on exploitation, drawing parallels with child sexual exploitation and 'modern slavery' that could inform further research.