DNA extracted from putrefied tissue or bloodstains may contain a co-purified contaminant, identified as the porphyrin compound (hematin). When contaminated but less degraded DNA was analyzed by PCR, it was necessary to eliminate the impurity by anion exchange column chromatography or chelating resin preparation, and ultrafiltration using Centricon microconcentrators. When highly degraded DNA was examined, trace amounts of high molecular weight DNA (HMWDNA) was recovered by electroelution method, and further purified by column chromatography and ultrafiltration. The amelogenin gene for sex determination could be amplified by dual PCR technique from samples purified by the above process. The results suggested, however, that the electroelution method was risky, time-consuming, and provided enhanced opportunity for sample contamination. 5 figures and 40 references