Abstract: Paraquat, PO (1,1'-dimethyle-4,4'-bipyridylium dichloride) is widely used herbicide known to cause fatal intoxication in both human and animals. This study was carried out to investigate additional information about the deleterious haematological, hepatic, renal and neurotoxicities of this herbicide on male guinea pigs. Animals were injected intraperitoneally with sublethal dose (1 mg kg–1 b.wt.). The tested parameters were determined after 7 days of PG injections. The data presented in this work showed that PO administration induced elevations in haematocrit values, while the number of blood platelets were decreased. The number of red blood cells, haemoglobin contents and total bilirubin concentrations showed no significant changes. It provoked sever perturbations in liver functions as indicated by inhibition of aspartate and alanine aminotransferase (AST), (ALT) activities. Paraquat administration resulted in marked impairment in the renal function as indicated by elevations in serum urea levels. The hepatic and renal dysfunctions lead to increases in serum total lipid and triglyceride concentrations. On the other hand, hypocholesterolaemia as well as hypoglycaemia were prominent. Also, significant decreases were demonstrated in serum total protein and albumin concentrations, while the serum globulins were significantly increased with unique declines in the measured serum cation concentrations (Fe3+, Na+ and K+) and the water content of blood, liver, kidney and lung. Serum uric acid concentrations and the water content of muscle are still at their normal levels. Paraquat administration revealed consipecious disturbances in acetyl cholinesterase (Ach El and creatin kinase (CK) activities. Also, this work was planned to evaluate the ability of either vitamin C (vit. C) or selenium (Se) to prevent or reduce its toxic effects. The results show that i.p. injection of vit. C (100 mg kg–1 b.wt.) was highly effective than Se (20 μ mol/kg b.wt.) in the protection against paraquat induced toxicity. The mode of toxic action of PG and the effect of either vit. C or Se in preventing or reducing these toxic effects were discussed in details. It is concluded that vit. C might be an important participant in the treatment of PO toxicity. Also, the treatment with vit. C should include a suitable hyperglycaemic drug.