📓 Colossal magnetoresistive (CMR) compounds with the perovskite structure are mainly characterized by a competition between ferromagnetism and paramagnatism, and between a metallic and insulator behavior.Electrical and structure have been studied in La1-xSrxMnOy (x = 0.1,0.15,0.2,0.25,0.3,0.35). The magnetoresistance was determined by measuring the temperature dependence of resistivity under a magnetic field 0.5 T. It was negative for all compositions and significantly influenced by the Sr content and annealing time. The obtained magnetoresitance values may make the materials promising for different applications.