Mercury is released from amalgam fillings in several forms, i.e. as elemental vapour, ions and in fine particles. Despite many investigations there is still considerable uncertainty concerning the uptake of such mercury. Most available estimates have calculated the pulmonary uptake of mercury vapour based on measurements of concentrations intra-orally or in expired breath. Presented estimates vary by an order of magnitude from approximately 1 to 20 micrograms/day. The possibility of estimating this uptake based on levels of mercury in a biological index medium has received comparatively little attention. The purpose of the present work is to estimate the uptake of mercury from amalgam fillings based on urinary concentrations of mercury. It is estimated that the average uptake of mercury from amalgam fillings in Swedish subjects is within the interval 4-19 micrograms/day. This interval was arrived at after a detailed evaluation of the uncertainties in the data used and in the different assumptions. Notwithstanding the considerable range of this estimate it indicates a higher uptake than several other estimates, some of which have had a large impact on the scientific debate concerning this issue.