The effects of the recycle of mass or energy on the control of chemical processes are studied. The recycle can be considered analogous to a feedback and significantly changes the characteristics of the process. The study on simple transfer function models indicates that the recycle loop gain strongly and time constant of the recycle unit somewhat less strongly influence the behaviour and the controllability of the process. Higher time constants of the recycle, the use of large surge tanks, and the control of the recycle unit of smaller time constants improves the range of stability. Two case studies, the distillation train of the manufacture of styrene and a simple reactor-distillation column system, demonstrate that chemical processes with internal recycle can usually be controlled with decentralised control structure with individually tuned controllers. The case studies also show that in the case of the control structure design the connections of the different units should be considered and the control of the recycle unit is also important.