A rhenium (Re) 188 conjugate of ethiodized oil (lipiodol), an iodinated ethyl ester derived from poppy seed oil, with potential antineoplastic activity. Upon hepatic intra-arterial injection rhenium Re 188 ethiodized oil accumulates in hepatocellular carcinoma (HCC) tumor cells, thereby delivering a cytotoxic dose of radiation through Re 188 directly to the tumor cells. This may kill tumor cells while sparing surrounding normal cells and tissues. Compared to iodine I 131, Re 188 has a shorter half-life.