INTRODUCTION Cyclophosphamide(Procytox or Cytoxan) is a drug used in the treatment of cancer, andis in a class of drugs known as alkylating agents. Cyclophosphamide(C 7 H 15 Cl 2 N 2 O 2 P ) is also used to treat bronchogenic carcinoma, small cell lung carcinoma, and other types of cancer 1-3 . It is obvious ,drug delivery technology modifies drug release profile, absorption, distribution and elimination for the benefit of ORIENTAL JOURNAL OF CHEMISTRY www.orientjchem.org An International Open Free Access, Peer Reviewed Research Journal ISSN: 0970-020 X CODEN: OJCHEG 2014, Vol. 30, No. (4): Pg. 1865-1875 Structural and Stability Investigation of the Anticancer Drug Cyclophosphamide via Quantum Chemical Calculations: A Nanotube Drug Delivery Z. FELEGARI* Department Of Chemistry, Science and Research Branch, Islamic Azad University, Tehran, Iran. *Corresponding author E-mail: z.felegari2014@gmail.com http://dx.doi.org/10.13005/ojc/300447 (Received: September 12, 2014; Accepted: October 04, 2014) ABSTRACT Cyclophosphamide is a medicine used to interfere with the growth and spread of tumor cells and treat cancers and autoimmune disorders.This work reports the study of anticancer drugs with density functional theory (DFT) and electronic structures.Its structure was optimized with B3LYP/6-311G* level in the gas phase and different solvents (SCRF calculation). NBO analysis,NMR parameter,thermodynamic properties,HOMO and LUMO,HOMO-LUMO band gap, and the electronic chemical potential (μ) were calculated. The results indicated that the Cyclophosphamide in water solvent is more stable than the gas phase orother solvents. Key words: Cyclophosphamide, NBO,NMR parameter,HOMO-LUMO gap,DFT. improving product efficacy and safety, as well as patient convenience and compliance 4-7 . For this reason many protein and peptide drugs have to be delivered by injection or a nanoneedlearray.Today efforts in the area of drug delivery include the development of targeted delivery in which the drug is only active in the target area of the body 8-11 . Cyclophosphamide is biotransformed principally into the liver to active alkylating