For some years research into the ?eld of drug formulation has focused on the systems that delay the release of drugs from the substrate. The reasons, among others, that have led to the formulation of sustained release drug delivery systems stem from the wish to achieve the slow release of highly water-soluble compounds, direct such compounds to the target organ or cell, achieve release rates that match a given aim, decrease the number of daily administrations, and improve compliance and minimize side effects. In this thesis, polyblend of agar and polyacrylonitrile nanofibers containing methotrexate has been electrospun to be used for controlled drug release in cancer treatment. To evaluate the effect of the polymer ratio on release rate, solutions with a fixed concentration of 15% polymer, 6% drug and different polymer solution blends of polacrylonitrile:agar ratios of 100:0, 90:10, 80:20 and 70:30 were prepared and the nanofibers were produced by electrospinning technique. Also, to evaluate the effect of the drug concentration, solutions with concentrations of 0%, 6%, 12% and 18% of drug-polymer weight ratio and constant ratio of two polymers (90:10) was prepared were electrospun. Scanning electron microscopy (SEM) was used to investigate the effect of polymer ratio and drug concentration on the morphology and average diameter of the electrospun nanofibers. The results showed that increasing the drug and agar percentage, will lead to an increase in the diameter, due to an increased in the viscosity. In order to study that no chemical intraction of the polymer and drug has taken place, FTIR spectrums were evaluated. DSC results were also studied to investigate the physical structure and chemical interactions. Drug release profiles were studied in phosphate buffer solution () with pH 7.4. Spectrophotometric method was used to determine the drug release rate by measuring the concentration in the released phase. The results suggested that increasing the drug concentration, significantly increases the release rate. After over 4 hours, the amount of drug released from nanofibers with 6% and 18% methotraxate concentrations, was 26.4% and 79.8%, respectively. Also by increasing the agar ratio in the solution blend mixture of polymers, due to increase in the polarity and hydrophilic of drug delivery systems, the drug release rates were increased. For example, in a sample with no agar, after 4 hours, 9.91% and in a sample containing 30% agar, 54% of the drug is released in the . According to the obtained results, it can be said that agar and poly acrylonitrile polyblend nanofibers can release methotrexate in a controlled manner, and the drug loaded nanofibers can be used as a locally controlled delivery system for methotrexate in cancer treatment. Also in this system, by changing factors such as the percentage of drug or agar, desired release rate can be achieved. Key Words controlled drug release, agar, polyacrylonitrile, nano fiber, methotrexate