Infinite layer Ca1-xSrxCuO2 (CSCO) films, grown by pulsed laser deposition with x=0.66 and 0.9, were doped by implanting O+ ions with an accelerating energy of 70 keV and a dose of 3×1016 cm-2. The resistivity of the films, in the temperature range 4–200 K, decreased by over two orders of magnitude compared with the original as‐grown film. Annealing the as‐grown films in an atmosphere of O2 at 500 °C resulted in only a factor of 2 decrease in this temperature range. A magnetic anomaly resembling a diamagnetic transition was observed in the 85–90 K range in implanted films which was not observed in as‐grown films. A comparison of the properties of implanted films, before and after annealing, suggest that increased oxygen content alone is not responsible for the observed changes, and thus defect creation resulting from implantation may also play a significant role. © 1995 American Institute of Physics.