A computational study of peristaltic micropumps is presented. The peristaltic micropump considered in this study consists of two to five chambers in series which rectify the flow by means of both peristaltic movement of actuators and diffuser/nozzle elements. We consider a closed loop configuration in order to reduce the error introduced by presence of inlet/outlet boundary conditions. The characteristics of these pumps such as maximum volume flux and pressure drop were investigated. In addition, the viability of such pumps to work with cells was examined by calculating the maximum shear stress and strain rate.