Concentrations of heavy metals (zinc, copper, cadmium, and iron) were measured in several tissues (brain, gizzard, leg-muscle, heart, breast-muscle, intestine, liver and kidney) of moorhens (Gallinula chloropus), black-headed gulls (Larus ridibundus), and coots (Fulica atra) collected between autumn 1985 and spring 1989 in northern Italy. Cadmium concentrations in the liver and kidney of water-rails (Rallus aquaticus) and in five species of Anatidae collected also were measured. High mean (+/- SD) copper levels were detected in aerobic muscles such as heart (38 +/- 5 micrograms/g dry weight (DW)) and pectoral muscles (35 +/- 7 micrograms/g DW). Compared to other tissues, the iron content of brain was rather low and constant, with a mean value of 160 +/- 17 micrograms/g DW in moorhens, 157 +/- 60 micrograms/g DW in black-headed gulls, and 157 +/- 25 micrograms/g DW in coots. Iron concentrations in tissues of moorhens from the Reno River were significantly higher than those from the Sile River. Cadmium was detectable only in the liver and kidney; there was a linear relationship between cadmium levels in these two organs. The highest mean (+/- SD) cadmium concentrations were present in the kidney of black-headed gull (30 +/- 20 micrograms/g DW).