It is known world-wide literature that seafood consumption is the main source of mercury intake in people not occupationally exposed. Several studies on the presence of mercury in sea water, sediment and fish and its effects on human health have been carried out in many countries in the Mediterranean area such as Greece, Italy and Jugoslavia. Few data have been published on Sicilian coastal population, consumers of high amounts of fish and on seawater status as the starting point of alimentary chains involving marine food. This study was carried out in July 1991 and July 1992 to determine total mercury and methylmercury levels in selected populations of the coast of Sicily: fishermen in a little island, Favignana, located west of Sicily, where the population can be considered at risk due to its high fish intake, and fishermen of a small fishing village (Porticello), near Palermo. As a control group, a sample population in a town located in the middle of Sicily (Valledolmo), where consumption of fish and seafood was quite inexistent and an urban population (inhabitants of Palermo) with variable quantities of seafood in diet were taken. Following the guidelines of WHO (1982) the subjects were interviewed by a dietary questionnaire. One hundred and twenty three hair samples, cut from the occipital area, were analysed for total mercury and methylmercury concentrations. Following the standard procotol for mercury analysis in hair, only those specimens exceeding 10 µg/g total Hg were analysed for methylmercury content. The results of study on 98 fishermen and their families with hair samples have shown that the dietetical weekly intake of seafood is related to the concentration values of total mercury and methylmercury that were found in the analysis. Only 19 subjects have been found with total mercury concentration values above the security level (> 6 µg/g total Hg) and 8 have been analysed for methylmercury. From our data, it appears that in this Sicilian area, when there aren't industrial and natural sources of Hg, even if the population eats a large amount of locally caught fish, the concentration of Hg found in hair samples never reaches risk levels.