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ORRCA ( is a free, online, searchable database of research around recruitment to Clinical Trials. It aims to help users identify promising recruitment interventions and inform the matching or tailoring of these interventions to specific recruitment challenges faced by different types of trial.


A team of international reviewers have screened nearly 69,000 articles identified through search engines and hand searches. Eligible articles include nested randomised control trials and systematic reviews of recruitment interventions, studies describing recruitment strategies, case reports of recruitment successes and failures and articles exploring reasons for participation.


The database currently contains over 3,500 articles covering recruitment within all continents and across all Health Research Categorisation System (HRCS) health categories. Users can identify relevant articles using free text searches of titles and abstracts or through using filters which include recruitment theme, health area, gender, age, location or research methods.


The database is being updated annually, but authors are welcome to submit new publications through the website. Work is also underway to extend the database to include retention research.


You can read about the development of ORRCA here.


Further information can be found at or via the recent publication in Clinical Trials (



archive  recruitment