The isolation of nucleic acids from a sample is an important step for many molecular biological applications and medical diagnostic assays. This protocol describes an efficient method for purification or/and isolation of nucleic acids from difficult animal tissues, plant material and other samples from which DNA extraction is generally regarded as being difficult which can contain impurities and inhibitors or interfering substances. This method is established acidic CTAB (with a pH value of 5 to 6.8) based extraction protocol that allows for reliable isolation of high molecular weight genomic DNA for removing contaminants from nucleic acids in a sample, e.g., environmental or biological samples such as soil, food, plant, animal or microorganism. DNA may quickly be extracted from samples without phenol, guanidine thiocyanate or 2-mercaptoethanol.