This work focuses on synthesizing nonlinear decoupling controllers for multivariable nonlinear systems represented by a state-space model, in the presence of deadtimes. The deadtimes appear in both the inputs and the outputs, but not in the states, and are physically associated with sensors and actuators. Simple sufficient conditions for feasibility of closed-loop deadtimes are derived, which rely only on the structural properties of the system. A control law is then derived so that the closed-loop system is input/output linear and decoupled, with deadtimes equal to the smallest ones that satisfy the feasibility conditions. The proposed method is applied to a chemical process. Its performance is evaluated through simulation in the presence of set-point and disturbance changes. (C) 2003 Elsevier Ltd. All rights reserved.