A method for locating a target comprises: a) receiving, by means of N≧1 receivers, opportunity radioelectric signals transmitted by M≧1 transmitters and reflected by the target, with N·M≧3, or at least one transmitter being situated out of sight of at least one receiver; b) receiving, by means of a data transmission link, one or more reference signals, representative of the radioelectric signals transmitted by each transmitter situated out of sight of at least one receiver; and c) determining the position of the target on the basis of the radioelectric signals and of the reference signal or of the reference signals. An application of the method to the primary monitoring of air traffic, a multistatic radar system for the implementation of the method, and a system for monitoring air traffic comprising a multistatic radar system are provided.