Cancer continues to increase with increasing age of the population.In a number of situations, the malignancy of tumors is detected only at advanced stages when administration of chemotherapeutic drugs is toxic to healthy cells.Carbon nanotubes (CNTs) comprised of thin sheets of benzene rings rolled up into the shape of seamless cylinders has recently attracted significant attention for use in biomedical applications [1-6].A limited number of single-wall metal-organic nanotubes (SWMONTs) have been synthesized, while a majority of reports have focused solely on structural details, SWMONTs have already shown promise in highly selective adsorptions [7].Both single-walled nanotubes (SWNT) and multi-walled nanotubes (MWNT) are being considered as a drug delivery nanoearrier [8], because they were observed to cross cell membranes [9-11] and exhibit blood circulation half-lives of the order of hours [12].The possible mechanisms proposed for CNT-drug interaction are: (a) the absorption of active components of drug within the CNT mesh, (b) non-covalent or covalent linkage of drug molecules, peptides, and nucleic acids to the exterior walls of the CNTs, and (c) the use of CNT channels as catheters.Herein, we used the reported self-assembled functionalized SWMONTs to realize drug delivery of 5-Fluorouracil (5-FU), which could be assigned to the first CNT-drug interaction [13].The characterization of the material indicated the presence of drug associated with SWMONTs (5FU@SWMONTs) in a proportion of 0.33 g 5-FU per 1.0 g of SWMONTs.The drug demonstrated a slow release profile where 79.6% of the drug was released in PBS buffer (pH7.4) in 24 hours, while 75% in PBS buffer (pH5.7) in 24 hours.The cytotoxic tests were carried out against two cell lines: 4T1 and RAW264.7.The highest lethality of cancer cells occurred at the highest concentration of 5FU@SWMONTs for the longest period of time.The results demonstrate that the cytotoxicity of 5FU@SWMONTs to cancer cells was improved by the SWMONTs component.