The effect of aqueous extract of Withania somnifera (L. Solanaceae) was studied against paclitaxel induced neutropenia in mice. After paclitaxel 1 mg/kg, i.v. administration significant fall in total WBC and absolute neutrophil count was observed on day 3 and day 5. W. Somnifera (200 mg/kg, p.o.) per se produced significant increase in neutrophil counts. W. somnifera (200 mg/kg, p.o.) when administered for 4 days before paclitaxel treatment and continued for 12 days caused significant reversal of neutropenia of paclitaxel. The findings of the study suggest the potential of W. somnifera as an adjuvant during cancer chemotherapy for the prevention of bone marrow depression associated with anticancer drugs.