Intellectual property is associated with the creative work needed to design clinical trials. Two approaches have developed to protect the intellectual property associated with multicentre trial protocols prior to site initiation. The 'open access' approach involves publishing the protocol, permitting easy access to the complete protocol. The main advantages of the open access approach are that the protocol is freely available to all stakeholders, permitting them to discuss the protocol widely with colleagues, assess the quality and rigour of the protocol, determine the feasibility of conducting the trial at their centre, and after trial completion, to evaluate the reported findings based on a full understanding of the protocol. The main potential disadvantage of this approach is the potential for plagiarism; however if that occurred, it should be easy to identify because of the open access to the original trial protocol, as well as ensure that appropriate sanctions are used to deal with plagiarism. The 'restricted access' approach involves the use of non-disclosure agreements, legal documents that must be signed between the trial lead centre and collaborative sites. Potential sites must guarantee they will not disclose any details of the study before they are permitted to access the protocol. The main advantages of the restricted access approach are for the lead institution and nominated principal investigator, who protect their intellectual property associated with the trial. The main disadvantages are that ownership of the protocol and intellectual property is assigned to the lead institution; defining who 'needs to know' about the study protocol is difficult; and the use of non-disclosure agreements involves review by lawyers and institutional representatives at each site before access is permitted to the protocol, significantly delaying study implementation and adding substantial indirect costs to research institutes. This extra step may discourage sites from joining a trial. It is possible that the restricted access approach may contribute to the failure of well-designed trials without any significant benefit in protecting intellectual property. Funding agencies should formalize rules around open versus restricted access to the study protocol just as they have around open access to results.