BACKGROUND AND OBJECTIVE: Multi-centre randomised controlled trials (RCTs) provide vital information about healthcare interventions. Reporting on country-level participation is important for understanding the context of multi-centre RCTs. This study aimed to examine multi-centre RCT reporting of country-level participation, using Ireland as a case study. STUDY DESIGN AND SETTING: This is meta-research study included RCTs identified in a previous study of Irish RCTs. The previous study involved searching six databases (inception-2018) for RCTs with participants recruited in Ireland: PubMed, Embase, Scopus, CINAHL, PsychINFO and the Cochrane Register of Controlled Trials. This current study focuses on multi-centre RCTs conducted on humans in healthcare settings with <
80% of participants recruited in Ireland. Outcome variables were trial characteristics and reporting rates for several variables, including: number of Irish centres, number of participants recruited in Ireland, and reporting use of relevant reporting guidelines. Descriptive statistics were used for analysis. RESULTS: Overall, 239 RCTs were included. The most common intervention was a drug (74.9% of RCTs). The most common clinical domain was the cardiovascular system (18.0%). Number of Irish centres was reported in 75.3% of RCTs, and number of participants recruited in Ireland in 27.2%. Among RCTs published after the CONSORT reporting guideline was published, 8.3% reported using a relevant reporting guideline. CONCLUSION: Our findings show deficits in reporting for multi-centre RCTs, particularly in reporting number of participants in Ireland and reporting use of relevant reporting guidelines. The development of a multi-centre trial extension to existing reporting guidelines may partly address country-level reporting issues.