Parallel and Parareal Deferred Corrections for Temporal Integration of PDEs Abstract: The prospect of parallelizing the numerical solution of PDEs in the time direction has interested computational scientists for decades but has never achieved near the success as parallelization in the spatial domain. The introduction of the parareal algorithm in 2001 rekindled interest in this area, but parareal has yet to be widely accepted. I will discuss the parareal algorithm and show how it can be considered one instance of a much more general class of parallel deferred corrections algorithms which promise improved parallel efficiency. The future prospects for combining spatial and temporal parallelization for large scale PDE simulations will be considered.