Applications were found recently where the analy- sis of dynamic systems with a special structure could be simp li- fied considerably by transforming them into equivalent syst ems having complex coefficients and half the number of poles. The design of controllers for such systems can be simplified in th e complex representation, but requires techniques suitable for systems with complex coefficients. In the paper, the extensi on of the classical root locus method to systems with complex coefficients is presented. The results are applied with some advantages to a three-phase controlled rectifier.