To obtain adapted versions for the Spanish population of a specific version of the Revised Illness Perception Questionnaire Revised (IPQ-R(e)) and the Brief Illness Perception Questionnaire (BIPQ), conceptually and linguistically equivalent to the original questionnaires.Cultural adaptation of questionnaires: linguistic validation.Five primary care centres and a tertiary hospital.A multidisciplinary team was selected. A pilot study was performed on 30 people with chronic diseases (hypertension, diabetes mellitus, stable ischaemic heart disease, asthma, chronic obstructive pulmonary disease or osteoarthritis)The project proceeded in 3 phases: I) Double forward-translation, II) Pilot study and III) Double back-translation. Three consensus meetings were held, one in each phase. Another meeting was held with one of the authors of the original questionnaire, where we knew about a short version, the BIPQ. It was also included in the study. Double forward and back-translations were performed and consensus was reached in both stages.Phase I) The majority of IPQ-R(e) items did not raise problems of translation. Phase II) In the pilot study we detected that patients found some difficulties in connection with the comprehension and self administration of some items. Therefore it was decided to employ trained interviewers, to introduce changes in the IPQ-R(e) format and vocabulary and to adapt a specific version with fewer items that solved most of these difficulties Phase III) Back-translations were very similar to the original version. The BIPQ forward and back-translation process caused no difficulties.After lingüistic validation, IPQ-R(e) and BIPQ versions conceptually and lingüistically equivalent to original instruments were obtained.