The effect of oral administration of aqueous extract of Chrysocoma ciliata leaves at 50, 100, 200 and 400 mg/kg body weight for 14 days on some biochemical parameters of male rats was investigated. Theextract did not have any significant effect (p > 0.05) on the serum concentrations of sodium, potassium, chloride, urea, calcium, albumin, magnesium, inorganic phosphorus, uric acid, globulin and total protein as well as the red blood cell (RBC), hemoglobin (Hb), packed cell volume (PCV), mean corpuscular volume (MCV), mean corpuscular hemoglobin concentration (MCHC) and red cell distribution width (RCW). While the WBC was reduced at 50 and 100 mg/kg body weight, the 200 and 400 mg/kg body weight increased the blood parameter. The 50, 100 and 200 decreased the MCV. The doses increased the levels of large unstained cells (LUC), neutrophils, eosinophils, serum alkaline phosphatase, gamma glutamyl transferase, alanine and aspartate aminotransaminases whereas the lymphocytes, basophils, serum total and conjugated bilirubin were decreased in the animals. Theplatelet levels fluctuated throughout the experimental period. The level of the monocyte was only increased at 100 mg/kg body weight of the extract. The 50, 100 and 200 mg/kg body weight of the extract decreased the serum cholesterol concentration in the animals, whereas the 400 mg/kg body weight increased the lipid parameter. Similarly, the 50, 100 and 200 mg/kg body weight also decreased the serum triacylglycerol of the animals. The HDL-C, LDL-C and atherogenic index compared favourably with the control. While there was no significant change at all the doses investigated in the kidney and heart-body weight ratios, the extract at 50 and 400 mg/kg body weight increased the liverbody weight ratio. In contrast, the 50, 100 and 200 mg/kg body weight decreased the testes-body weight ratio. The parameter and dose specific effect of the extract on the biochemical parameters suggest selective toxicity