The possible benefits of using microchannel reactors in the chemical process industries have been under discussion for several years. Outstanding heat transfer properties, short residence times and short diffusion lengths are considered key advantages, while the cost of the approach and the pending question of long-term stability are still major sources of skepticism. A good starting point for a feasibility study is to investigate some major fluid dynamic properties. For a unit consisting of hundreds of parallel microchannels, the pressure drop for the laminar flow is just a few millibar. However, at high gas flows the distribution over the numerous channels may become non uniform. It is shown how the resulting residence time distribution affects both the yield of intermediates in consecutive reactions, and step functions of the concentration during periodic operation, respectively. All in all, the results of the estimations are encouraging.