Abstract: The 13 tissues ( liver, kidney, muscle, bone, skin, heart , lung, intestine, blubber, spleen, pancreas, fore stomach and main stomach) of 22 Dall. s porpoise ( Phocoenoides dalli ) ( 11 ` and 11 a ) off Sanriku coast of northern Japan were measured for iron ( Fe) bioavailability. Particularly higher Fe concentrations were found in the lung, liver and spleen than the remains. Lower Fe concentrat ions were recorded in skin and blubber. Hepatic Fe concentration positively correlated with maximum duration of dives among cetacean species ( y= 285. 17x 0. 5267 ; r 2 = 0. 92; y : average hepatic Fe concentrations in Lg#g - 1 dry weight; x : maximum diving duration in min) . Using this correlation, the maximum duration of dives of Dall. s porpoise was estimated as 11. 85 min.