Kidney and spleen tissues from flounder Platichthys flesus (L.) collected from Neal Point in the estuary of the river Tamar were examined by x-ray microanalysis for the presence of heavy metals within the melanomacrophage centres. Ultrastructurally these centres consisted of groups of pigment-containing macrophages in which melanin was the most prominent pigment, but lipofuscin and haemosiderin were also present. Some of the macrophages also contained irregular metal particles and minerals with associated metals. The metals identified within these inclusions were Ti, Cr, Fe, Co, Ni, Cu, Zn, Sr, Ag, Sn, Ba, La, Ce, Nd, W, Au, Pb, Th and U. The results are discussed in relation to the sediment chemistry of the River Tamar, and the possible routes of uptake by the fish.