Sulfur is one of the most reactive chemical elements, The EPA (environmental protection agency) has labeled elemental sulfur as generally safe. This study sheds light on the ability of sulfur to cause toxic biochemical effects by measuring biochemical changes in many parameters. The activity of alanine aminotransferase (ALT) and aspartate aminotransferase(AST), Glutathione (GSH) and Malondialdehyde (MDA) and glucose in blood plasma, brain, and liver of mice. Mice were orally dosed with sulfur at doses of 4 and 8 kg b.wt. which significantly decreased blood sugar level, ALT, and AST activity at 8 g/kg .in blood plasma after 4 and 1 day. On the other hand, administration of sulfur at doses of 1 and 4 g/kg b.wt, after 7 and 14 days of repeated treatment with it led to a significant decrease in the level of GSH in blood plasma and liver of mice with a significant increase in the level of GSH in the brain, while the 3doses of sulfur caused a significant increase of MDA level in blood plasma, brain, and liver of treated mice. The results of our follow-up testing also showed the biochemical effects of sulfur on both ALT and AST enzymes; it showed a slight increase in the level of both enzymes in blood plasma and a significant decrease in the level of brain GSH after 24 hrs of treatment. In contrast, the level of brain GSH significantly increased after 14 days of sulfur dosing, with a significant increase in the activity of both enzymes(ALT, AST) which indicates the persistence of the toxic effect on the liver. We conclude from this study the possibility and ability of sulfur to cause toxic biochemical effects in mice.