A parallel control system, consisting of a bank of concurrently running virtual control loops and a concurrency coordinator, is proposed for plants that operate in multiple, often radically different regimes. The virtual control loops acting in parallel and exchanging information among themselves, are coordinated to obtain good closed-loop performance in each operating regime, and bumpless transfer during transitions. The basic strategy, overall structure, and the individual elements of the parallel control system are discussed; the design, analysis, and performance are illustrated via simulation of a chemical reactor designed to manufacture product in three different regimes.