Total and organic mercury concentrations were determined in the liver, kidney, muscle, skin, brain and blubber collected from 12 common dolphins, Delphinus delphis, stranded along the Portuguese coast between 1998 and 2003. The liver was the preferential organ for Hg accumulation, while the lowest values were detected in the blubber. Total and organic Hg concentrations in the liver, skin and blubber of dolphins were positively correlated to the levels found in muscle. Positive correlations were also observed between liver and kidney, and skin and blubber. Muscle levels increased linearly with length, while those of liver and kidney varied exponentially for skin, brain and blubber, were sparse. The percentage of organic Hg decreased linearly with length in muscle and exponentially in liver and kidney, accounting for only 10-30% of the total Hg in adults. The concentrations found in this work were lower than those reported by other authors for the same species from southern European coasts. [ABSTRACT FROM AUTHOR]