The effect of ethanolic extract of Bougainvillea spectabilis
leaves on some haematological and serum lipid parameters in rats during a seven day administration of the doses of 50,100 and 200mg/kg body weight orally was investigated. The parameters evaluated include serum lipids, red and white blood cell indices. The results show that the extract administered significantly reduced (P<0.05) packed cell volume, haemoglobin concentration and red blood cell count at the dose of 200mg /kg body weight when compared with controls while other doses administered had no significant effect (P<0.05) on these parameters. Also, the extract significantly reduced (P<0.05) white blood cell count at all doses administered when compared with control. However, the extract had no significant effect (P>0.05) on MCH, MCHC, MCV and platelet count when compared with controls. Moreover, the extract significantly reduced (P<0.05) total cholesterol concentration in the serum while it had no significant effect (P>0.05) on serum HDL-cholesterol concentration at all doses administered when compared with controls. However, the extract significantly increased (P<0.05) serum triacylglycerol concentration at the dose of 50mg/kg body weight while other doses administered had no significant effect (P>0.05) on serum triacylglycerol concentration. The results of this study suggest that the extract may have beneficial effect on serum cholesterol concentration reduction, although it possibly possesses the potential of adversely affecting haematological indices.