The invention related to a method for the stabilization, purification or/and isolation of nucleic acids from material samples, in particular, stool samples, which can contain impurities and inhibitors or interfering substances. The invention further relates to a reagent kit for carrying out this method. The basis of the invention is, in particular, a method for purification, stabilization or/and isolation of nucleic acids from material samples, whereby a buffer is added to the sample containing the nucleic acids, with a pH value of 2 to 7, a salt concentration of at least 100 mM, or/and a phenol neutralizing substance. According to the invention, pure nucleic acids which may be amplified can be obtained from faecal samples by a simple method, which are suitable for diagnostic proof of infection, in particular, bacterial or viral infection, or mutation, in particular, for tumor-specific DNA mutations.