No tools are available to assess or measure the experience of chemotherapy-induced nausea and vomiting (CINV) for Persian/Farsi speakers. The purpose of this study is to translate the Rhodes Index of Nausea, Vomiting and Retching (INVR) scale for use with Persian-speaking cancer patients. A sample of 94 cancer patients were recruited from a cancer research centre in Mashhad-Iran. A standard two phase process of scale translation and validation was conducted. In phase I, standard 'forward- backward' translation procedure was used to translate the original version of the INVR questionnaire into Persian. The translated questionnaire was reviewed and revised and a Persian version of the scale was produced. In the second phase, a multiphase instrumentation study describing the internal consistency and test-retest reliability of the translated version was conducted. The inter-item correlation measured by Cronbach's alpha was 0.88. Test/re-test reliability was measured by the weighted kappa and was between 0.63 and 0.79, indicating 'substantial agreement' and stability between the initial and subsequent administrations for each item. These results demonstrate that the Persian version of the INVR is acceptable for use among Iranian cancer patients. Researchers could use this study as a model for future translation and application of psychometric instrumentation.