Background: When national pharmacoeconomic guidelines are compared, different recommendations are identified on how to identify, measure and value lost productivity, leading to difficulties when comparing lost productivity estimates across countries. From a transferability point of view, the question arises of whether differences between countries regarding lost productivity are the result of using different calculation methods (methodological differences) or of other between-country differences. When lost productivity data differ significantly across countries, the transferability of lost productivity data across countries is hindered. Objective: The objective of this study was to investigate whether country of residence has a significant influence on the quantity of lost productivity among patients with rheumatic disorders. Confounding factors that might differ between countries were corrected for, while the methodology used to identify and measure lost productivity was kept the same. Methods: This question was investigated by means of an online questionnaire filled out by 200 respondents with a rheumatic disorder per country in four European countries, namely the Netherlands, the UK, Germany and France. In addition to those regarding lost productivity, the questionnaire contained questions about patient characteristics, disability insurance, disease characteristics, quality of life and job characteristics as these variables are expected to influence lost productivity in terms of absenteeism and presenteeism. The data were analysed by regression analyses, in which different components - being absent in last 3 months, number of days absent and presenteeism - of lost productivity were the main outcome measures and other variables, such as gender, impact of disease, shift work, job control, partial disability and overall general health, were corrected for. Results: The results showed that country sometimes has a significant influence on lost productivity and that other variables such as, for example, age, disease severity, number of contract hours, decision latitude, experienced health (as reported on the visual analogue scale) and partial disability, also influence lost productivity. A significant influence of country of residence was found on the variables 'being absent in the last three months', 'number of days absent' and 'quality of work on the last working day'. However, country did not influence 'quantity of work on the last working day' and 'overall presenteeism on the last working day'. Conclusion: It can be concluded that country has a significant influence on lost productivity among patients with rheumatic disorders, when corrected for other variables that have an influence on absenteeism and presenteeism. Transferring lost productivity data across countries without adaptation is hindered by the significant differences between countries in this patient group. As a result, transferring lost productivity data, being either monetary values or volumes of productivity losses, between countries can give wrong estimations of the cost effectiveness of treatments.