Earthworms are important organisms for the soil system because they perform favourable effects on soil structure and functions (Jongmans et al., 2003). Earthworms are abundant in soil, easy to maintain in laboratory conditions, and sensitive to toxic chemicals (OECD guidelines, 1984, 2004); for these reasons they represent useful bioindicator organisms for Environmental Risk Assessment of the soil. In recent years the use of earthworms biological responses (i.e. biomarker) to chemical pollutants has known a growing interest for polluted soil risk assessment. The aim of this research was to investigate a novel potential biomarker, such as morphometrical alteration of coelomocytes, together with other standardized biomarkers and ecological endopoints in the common earthworms Lumbricus terrestris exposed to copper sulphate or methiocarb. The study was carried out in laboratory and in field conditions. A significant (P<0.001) enlargement of coelomocytes was found either in CuSO4 or methiocarb exposed animals; celomocyte alteration showed a good correlation with the other standardized biomarkers and the analyzed ecological endpoints. Results obtained in standardised laboratory conditions were validated in field conditions. In conclusions obtained results suggest the potential application of pollutant induced morphometrical alteration of earthworm coelomocytes as biomarker of general stress suitable to be used in a battery of biomarkers in soil environmental monitoring programmes.