The presence of recycle streams in chemical plants and their implications in the design of the control system are analysed referring to different processes. Main effects consist in amplification of disturbances, changes of the process dynamics and interactions. By decomposing the global plant in a process without recycle and in a recycle process, a compensator can be designed to be added to a controller designed for the process without recycle. The achievable performance is compared with a control system specifically designed for the global process including the recycle. Ease of design and superior performance for the structure based on the compensator are clearly shown for a simple case and are retained in the application to a multivariable case. Also the effect of modelling errors and variations in the recycle flow rate are examined.