The present study deals with the cytotoxic activity of the ethanolic root extract of C. gigantea Linn. The different concentrations of ethanolic extract of the roots of C. gigantea Linn were used for cytotoxic activity by Brine shrimp lethality bioassay (BSLB) and Allium cepa root meristem (ACRM) models. In BSLB, LC50 value was found to be 62.12μg/ml while LC50 value of cyclophosphamide was found to be 41.54μg/ml. In ACRM model, incubation of onion bulbs in different concentrations of extract produced a growth retarding effect that was associated with a decrease in the root number. ACRM growth inhibition was highest with significance of (p<0.01) at the 10 mg/ml concentration after 48 hrs incubation for ethanolic root extract. Extract produced dose and time dependent growth inhibition. The ethanolic root extract of C. gigantea exhibits potent cytotoxic property comparable to that of standard drug. Therefore, this might be utilized for the development of novel anticancer drug leads.