Every cell in our body contains genetic information for its proper functioning. This information is present in the long stretch of nucleotides—adenosine (A), cytosine (C), guanosine (G), and thymidine (T)—that form our DNA (deoxyribonucleic acid). Several hundreds to thousands of these A, C, G, and T nucleotides contain the information for one gene, and our DNA contains more than 30,000 genes. Each of these genes has to be intact for proper functioning. However, the integrity of our DNA is threatened by many different agents, such as sunlight, chemicals, and even the oxygen in the air. If damaged DNA were left unrepaired, the cells of our body would quickly lose essential gene functions and life would not be possible. However, all living organisms contain a multitude of enzymes that counteract such damage and restore the proper DNA sequence. Failure of these DNA repair functions can lead to various diseases, such as cancer and developmental disorders. In recent years, considerable progress has been made in understanding the various DNA repair pathways. We are now on the verge of an era in which this knowledge can be exploited to develop more effective and specific anticancer drugs.