In the present paper, the procedure of back-to-back starting of pumped-storage hydraulic generating units is investigated and analyzed. The results from simulation as well as from real on-site measurements are presented and compared for a case study of a Greek power station. Main parameters influencing this phenomenon are analyzed, and information is given on the physical laws underlying the process. In particular, the effects of excitation and gate valve opening procedure are discussed, along with the torque-speed characteristic of the driving machine. Guidance is developed for the proper selection of the main parameters for a successful start.