BACKGROUND Within the framework of Codex Alimentarius, attempts are being made at international level to establish guidelines for use of nutrition and health claims. An important issue that has to be addressed is the process of scientific substantiating of claims on foods. OBJECTIVE To provide an insight into the current step procedure of the proposed draft recommendations on the scientific basis of health claims. These Codex recommendations are intended to facilitate governments' own evaluation of health claims made by the industry. METHODS Review of comments of governments, observers and non-governmental organizations (NGOs) and relevant references to the proposed draft recommendations of the last sessions of the Codex Committee on Nutrition and Food for Special Dietary Uses (CCNFSDU). A literature search was performed using the PubMed database. CONCLUSIONS Several proposed draft recommendations on the scientific substantiation of health claims have been considered and amended by the CCNFSDU in recent years but the work is not yet complete. The current work draws on the work of FUFOSE and PASSCLAIM and also on that of WHO and FDA. Given the important role of Codex in food safety, the draft recommendations emphasize circumstances where additional evaluation of safety or nutritional safety needs to be considered. High quality human intervention studies are the prime evidence needed to substantiate claims but there is recognition that, in some cases, only observational studies may be available. Animal and in vitro studies will also be evaluated as part of the totality of the evidence. It has been suggested that the recommendations should include re-evaluation of claims after a certain time period, or if new evidence calls into question the scientific validity underpinning the claims. Setting out a common approach for the substantiation of health claims is an important step in the use of health claims around the world. There is a need to reflect emerging as well as consensus science. The substantiating evidence should be proportionate to the claim. Further progress in the elaboration of this relevant Codex text is needed to reach consensus.