Anthracycline antibiotics are among the most effective antineoplastic agents. However, despite their high efficacy in the treatment of various types of cancer, their administration is limited primarily because they exhibit myocardial toxicity. This may be a limiting factor in the dosage of medications; nevertheless, drugs exhibiting this mechanism of action constitute a very important group of chemotherapeutics. One of the more widely studied antibiotics from the anthracycline group is doxorubicin. It exhibits the highest antineoplastic activity from among a number of derivative compounds. Because of the adverse effects of doxorubicin, especially cardiotoxicity, it is important to maintain control of its concentration in body fluids. The aim of the presented work is a method for rapid, simple and accurate determination of the level of doxorubicin in blood and plasma using spectrophotometric methods. The method consists in the study of the absorbance of light in the visible light range in a DOX solution with respect to a reference sample. Characteristic peaks are selected from the absorbance spectrum, and for those peaks the wavelength at which maximum absorption occurs is determined. The concentration of the analyte is determined by comparison with the calibration curve.