The electrical behaviour of La2_JtSrJ.Cu04_v solid solutions (with x = 0, x = 0.025, x = 0.05, and x = 0.15) at temperatures between 10 and 900 K and under different oxygen partial pressure pQl — 1 -M0~6 atm) has been investigated. The samples prepared and measured under an 0 2 flux (i.e~, with y = 0) show a superconducting transition with Tc = 46, 29. 37 K for x = 0. 0.05 and"0.15, respectively. The samples with x = 0.025, y = 0, and x = 0, y = t= 0 exhibit no sign of superconductivity. In the temperature range 100-900 K. La2Cu04 is semiconducting, whereas the electrical resistivity is independent of temperature for the x =0.025 sample, and the x = 0.05 and x = 0.15 are metallic.