Objective To investigate the effect of antitumor activity of ethanolic extract of Euphorbia thymifolia Linn. on lipid-lowering activity in transplanted fibrosarcoma in Wistar albino rats.Method Methylcholantherene-induced fibrosarcoma was transferred into rats. After the 30th day when the tumor became palpable ethanolic extract of Euphorbia thymifolia was used for the treatment by oral route for 20 days. On the 21st day samples of blood were collected and the organs like kidney and liver were used for estimation of very-low-density lipoprotein VLDL high-density lipoprotein HDL triglycerides and total cholesterol.Results Substantial reduction in the levels of lipids in serum like VLDL HDL triglycerides and total cholesterol was observed in tumor-bearing rats. It was found that the treatment with Euphorbia thymifolia 500 mgkg reduced these parameters to normal levels. When checked in the kidney and liver a considerable reduction in VLDL HDL triglycerides and total cholesterol were detected in the tumor-bearing rats. Euphorbia thymifolia 500 mgkg normalized the levels of all the parameters tested however this was only partially achieved with the lower dose 250 mgkg.Conclusion It was observed that in rats treated with Euphorbia thymifolia the altered lipid levels returned to normal values. Results of the present study suggested that the ethanolic extract of Euphorbia thymifolia Linn. exhibited an effective antitumor activity.