A multidisciplinary group (representing various professional bodies and supported by the Cystic Fibrosis Trust) has developed evidence-based guidelines for the performance of the sweat test in the UK. The guidelines cover patient information, subject suitability, sweat collection, sweat analysis, quality, interpretation of results, and responsibility for testing and training. The guidelines were produced following a detailed literature search by the process described by the Royal College of Paediatrics and Child Health (RCPCH), using the Scottish Intercollegiate Guidelines Network 1 (SIGN 1) criteria to grade the evidence. Recommendations are graded A, B, or C, depending on the level of evidence. The grade B recommendations (there were no grade A recommendations) were subsequently appraised and endorsed as part of the RCPCH process, according to Appraisal of Guidelines for Research and Evaluation in Europe (AGREE). The recommendations are summarized in tabular form representing the final version incorporating the comments from the appraisal process. Both the appraisal comments and the full evidence base can be found on www.rcpch.ac.uk/publications/clinical_docs.html. The full guidelines can also be found on http://www.ukneqas.org.uk/guidelines.htm.