AIMS: To assess, in relation to gaming machines, the level of consensus regarding factors which determine gambling-related harm; identify preventative measures which may be appropriate to the British context; and, to the extent that evidence was lacking or needed, recommend medium and long-term priorities for a programme of research to examine gaming machine players' behaviour and identify potential challenges associated with such research. METHODS: Consult international and British experts in a four-wave panel discussion. FINDINGS: There was broad consensus that high-stake machines are associated with problem gambling, but limited empirical evidence on game speed, distribution of wins, percentage return to player and structural factors such as stake and prize size or game speed. Accessibility was suggested to be related to harm. Harm mitigation measures discussed and supported by the panels include upper limits to stake sizes, extended control for the player over their expenditure, restrictions on 'autoplay' and reducing reel spin speed, restricting access to ATMs in gambling venues. Five key research topics prioritised were player control technologies; the impact access to funds; the impact of structural features; the role of socio-spatial and cultural environment; and development of gaming machine related harm. British experts highlighted the distinctiveness of the British gaming machine industry and regulatory framework and expressed concern that the industry would not be co-operative. RECOMMENDATIONS: A partnership should be facilitated between the gambling industry and other stakeholders in order to obtain access to various forms of data that could be analysed and to venues for research. Research using online gambling data may may give indivative answers to questions about structural features until the sufficient data is available for analysis from land-based gaming machines.