Carrier lifetimes in semiconductors have been recently rediscovered by the silicon IC community. This is an opportune time to discuss this topic since lifetime is emerging as an important parameter for describing material, process, and equipment cleanliness after being ignored for many years. This article tries to shed some light on "lifetimes in semiconductors," which is a topic that has caused much confusion in the past. Various recombination mechanisms are discussed and the concept of recombination and generation lifetime is presented. We will show that surface recombination/generation plays an important role in today's high-purity Si and will become yet more important as bulk impurity densities in Si are reduced further.