5-Chloro-2'-deoxyuridine (CldU) is a thymidine analog that is readily incorporated, following phosphorylation, into newly synthesized DNA in place of thymidine. Like 5-bromo-2’-deoxyuridine and 5-iodo-2’-deoxyuridine, CldU can be detected immunologically in cells and tissues. CldU can also be added to cells or tissues sequentially with another thymidine analog to label temporally distinct populations. The insertion of thymidine analogs, including CldU, can significantly alter DNA processing and replication, so these analogs have also been used as mutagens, clastogens, and antiviral compounds.
