There has been increasing uneasiness with the health authorities recently about the almost ubiquitous presence of organohalogenated compounds in drinking waters. The scientific interest in trihalomethanes (THMs) has increased since their carcinogenic properties were ascertained. For this reason several countries have set upper limits and guidelines for the total amount of THMs allowed in drinking waters which vary from country to country. Aiming at a better understanding of the maximum acceptable concentrations of THMs in drinking waters and considering the wide range of reported values in different countries, it has been considered useful to carry out a study on the presence of THMs in some Sardinian waters. This paper is an attempt at evaluating the THM concentration in the water distributed in the different villages; the final remarks will serve as premises for future studies both on the factors inducing such formation and on problems of risk for human health.