Shower Monte Carlo programs are indispensable tools for today's high energy physics phenomenology. In recent years, methods to improve these generators with the inclusion of Next-to-Leading order QCD effects have been put forward, and are actually being used by the experimental collaborations. In this talk I will illustrate the basic features of these methods, and I will review their status.
I will then discuss a few issues related to their use, especially in regard to the estimate of theoretical uncertainties.