Background concentrations of Fe, Mn, Cu, Zn, Pb, Cd, and Ni were calculated for brown algae Costaria costata from the northwest Sea of Japan. Also the paper contains refined data on heavy metal concentrations in the widespread distributed brown algae, such as Stephanocystis crassipes, Sargassum pallidum and S. miyabei. As the upper threshold levels of metal background concentrations, the median values plus double medians of absolute deviations from the medians were used (Me + 2MAD). The lower threshold level of the background concentration equal to the physiological need for an element is the median of 15% minimum values in the sampling minus the double median of absolute deviations from the median (Me₁₅ - 2MAD₁₅). The calculated ranges of the background concentrations of metals in algae were compared with concentrations of elements in mac-rophytes collected from habitats with background concentrations of metals in water.