Tests based on the PCR technique have the advantage to be rapid and highly specific, but, when applied on fecal samples, they lack sensitivity. This is probably due to different kind of problems: difficulty in lysing the cell wall, presence of inhibitory substances, not suitable conditions of the PCR reaction. We have taken into consideration the three kinds of problems, obtaining good results by the use of physical methods of lysys, in combination with a commercial DNA extraction kit (QIAamp stool mini-kit, Qiagen) and by the optimisation of the reaction conditions (MgCl2, BSA, Taq DNA Polymerase concentration and number of cycles).