Magnetic guidance of magnetic emulsion for site specific delivery was investigated in vitro and in vivo. The magnetic emulsion was characterized in vitro for its magnetic responsiveness using a constant flow apparatus, and its high retention by magnetic field was confirmed. After intravenous injection in rat, magnetic emulsions were localized to the predetermined site (lungs) by application of an electromagnet to the lungs. Similarly, 1-(2-chloroethyl)-3-(trans-4-methylcyclohexyl)-1-nitrosourea (methyl-CCNU) contained in the dispersed oily phase of the emulsions, was also concentrated at the target-site. Such preferential localization by magnetic means suggested that magnetic emulsions could become effective drug carriers with site specificity for the delivery of chemotherapeutic agents in cancer chemotherapy.