Pulsed laser deposition was used to grow c‐axis aligned films of La2−xSrxCuO4−δ, with Sr content, x, in the range of 0.03 to 0.2, on substrates prepared from single‐crystalline SrLaAlO4, with a lattice mismatch of 0.5%. The thickness dependence of Tc0, the temperature at which the resistance falls to zero, is much reduced compared to that of films deposited on SrTiO3, where the lattice mismatch is 3.4%. The maximum Tc0 is achieved at x=0.15 for both types of substrates. While the thickness dependence is related to the strain resulting from the lattice mismatch, the value of the maximum Tc0 is determined by the oxygen concentration. © 1994 American Institute of Physics.