The effect of aqueous extract of Ocimum gratissimum
on hematological parameters of Wister rats was studied. Twenty five rats with weight ranging between 100-160g were used. The rats were divided into five groups; with group one as the control group. Increasing doses (0.2, 0.4, 0.8, 1.6g kg-1
body weight) of the extract were administered orally to the other four groups for a period of four weeks. Significant (P< 0.05) decreases in the level of hemoglobin (Hb), packed cell volume (PCV), red blood cells (RBC), white blood cells (WBC) and other hematological parameters were observed.