Effects of endosulfan (EN), an insecticide, and bleomycin (BL), an antibiotic, on the body weight in the normal mice, and the in vivo cell growth, tumor weight, and hematological parameters of the Ehrlich ascites carcinoma (EAC) cell-bearing Swiss albino mice Mus musculus were evaluated. EN and BL were respectively administered orally and intraperitoneally to the experimental mice; the control group consisted of EAC cell-bearing untreated mice only. EN reduced the body weight in normal mice, whereas BL resulted in a steady body weight compared to the control. EN increased the EAC cell count significantly by reducing the growth of normal viable cells. In contrast, BL reduced the cell count by increasing the proportion of viable cells in the body. The tumor weights induced by EN were significantly higher than those of the EAC control and the BL-treated animals. In comparisons with the control and the BL mice, hematological parameters such as hemoglobin (%) and the number of RBC and lymphocytes were lowered, while counts of WBC, neutrophils, and monocytes were elevated after EN treatments. These results show that BL is capable of reducing the EN-induced neoplastic and haematological alterations in the mice under laboratory conditions.