Most viral treatments target the virus itself, providing very specific effects and limiting side-effects on uninfected cells. However, this strategy of drug design often results in resistant viruses, especially among RNA viruses. Therefore, the focus has turned to drugs that target cellular proteins that are essential for viral replication, but not for cellular viability. Pharmacological CDK inhibitors are a prime example of this type of approach. Reviewed within are the various functions of CDKs, their role in the life cycle of selected Retroviruses and Herpesviruses, and the pharmacological CDK inhibitors that have been focused on in terms of viral inhibition.