Abstract: Clinical reports on trivalent antimonyl ammonium gluconate (AAG) in the therapy of Schistosomiasis Japonieum revealed certain advantages of this compound over tartar emetic. This prompted a study of some factors which may alter the toxicity of this compound. The LD₅₀ of AAG after intraperitoneal injection in 10、20 and 30 grams mice were found to be 155、160 and 137 mg/kg respectively. For mice of 3.5、5.5、7.5 and 9.5 weeks of age, the LD₅₀ were respectively 114、123、117 and 123 mg/kg. The difference is not statistically significant. AAG did not show a sex difference in toxicity in 3.5、7.5 and 9.5 week old mice; but in 5.5 week old mice, AAG did show a higher toxicity in females than in males. For example, in one experiment the LD₅₀ for female mice was 110(102-118) mg/kg, whereas that for males was 140(123-147) mg/kg. At temperatures of 4℃、10℃、20℃、24℃ and 30℃, the LD₅₀ of AAG were 160、147、122、117 and 94 mg/kg respectively. It is likely that AAG is more toxic at higher room temperature than at lower temperatures. The intravenous, intramuscular and intraperitoneal LD₅₀ of AAG were approximately the same (123-150 mg/kg), whereas the oral LD₅₀ was about eight times as high (1000 mg/kg). The intraperitoneal LD₅₀ of AAG was 120(114-125) mg/kg for mice on a normal diet, 96(87-105) mg/kg for mice on a diet low in protein and 150(141-173) mg/kg for animals fed a high protein diet. The acute toxicity of AAG is independent of its antimony content since the intraperitoneal LD₅₀ were respectively 102、105、92 and 105 mg/kg for AAG containing 12.2% 18.7%、33.5% and 41.0% of antimony.