We have developed a delay-line parallel-plate avalanche counter (PPAC) with high detection efficiency for high-energy light ions. A large signal-to-noise ratio was achieved by a newly designed pre-amplifier and the usage of C 3 F 8 gas at a pressure of 30Torr. The counter has been tested with beams of 90AMeV 7 Li at RIKEN, 340AMeV 1 2 C at GSI, and 254AMeV 8 B at GSI. We achieved high detection efficiencies (>95%) for all of these ions. Furthermore, we achieved reasonable position and timing resolutions.