Pooling in HTS refers to the act of testing mixtures of compounds in a primary screen to accurately identify hits for secondary screening. The reduction in the number of tests needed to screen a compound library by pooling can also be extended to achieve much-needed error tolerance in HTS. Despite the success of HTS in other biological experiments, pooling in high-throughput drug screening has been a controversial and often marginalized paradigm. At first appearance, pooling appears to promise gains from reduced effort, or possibly could create more problems than solutions. However, this article demonstrates that pooling is a practical and necessary part of HTS: discussions include the rationale for pooling compounds in HTS, a unifying view of pooling design theory, a review of past attempts at pooling and their success, and recent advances in the field.