In this article, we investigate the thermal degradation of deoxyribonucleic acid (DNA). We find that under dry conditions, complete DNA degradation occurs at above 190°C. In addition, as the boiling temperature of water is pressure dependent, we have investigated the thermal degradation of the DNA in water for different applied partial pressures. This information is important for fundamental understanding of DNA structure and energetics, and can be useful for biomedical applications such as thermal targeting of DNA in cancer cells, as well as for basic research.