The aim of the study was to determine the toxicity of lysate macrocysts inoculum of Sarcocystis aucheniae (LMSA) in house mice (n=36) at concentrations of 5 and 10% (0, 50 and 100 mg of protein per gram of body weight) in doses of 0.5 and 1.0 ml. Rectal temperature, respiratory rate and survival rate plus histopathological changes in liver, kidney, heart, and lung were evaluated. All treated mice died within 4 to 20 hours after inoculation, showing hypothermia, dyspnea and bradypnea. The kidney and liver were most affected organs, showing severe hyperemia, tissue degeneration and hyperplasia. The mice in the control group showed no visible abnormalities or death. The results showed toxicity and lethality due to the lysate macrocysts inoculum of Sarcocystis aucheniae in house mice.