OBJECTIVES: The Patient eDiary is an 11 item electronic diary developed in US English by Boehringer Ingelheim to collect data for group comparisons of subjects with Chronic Obstructive Pulmonary Disease (COPD). The Patient eDiary was translated into 55 languages for utilization in an international study. A rigorous methodology was required to ensure conceptual equivalence and cultural relevance across languages within the constraints of the handheld electronic device via which the questionnaire is administered. METHODS: The translation process was conducted by specialists in each target country, following a standardized methodology: 1) two independent forward translations by native target language speakers; 2) comparison and reconciliation of the translations; 3) back translation by a native English speaker; 4) comparison of original and back translation; 5) review by a clinician; and 6) comprehension test on 5 COPD patients. RESULTS: The major challenge was finding conceptually equivalent and culturally relevant formulations which fitted into the limited space of 79 characters per screen provided by the handheld device. This was manageable for languages using the Roman alphabet although the structure of some require between 10 to 15 % more characters than English to convey the same notion. The characters of languages using a different script had to be reduced to 45 per screen given the size and space they require. A high percentage of abbreviations had to be used and careful testing was essential to ascertain comprehension by the target population. Examples of these and other constraints will be discussed in the presentation.   CONCLUSIONS: The 55 language versions of the Patient eDiary were established according to a rigorous methodology to ensure conceptual equivalence and cultural relevance across languages within the constraints of the handheld device. The Patient eDiary may now be used confidently for comparison of results and pooling of data in international studies involving COPD patients.