- In the present study we used microscopic Fourier-Transform Infrared spectroscopy (FTIR) to investigate and to detect malignant cells which were transformed in culture by murine sarcoma virus (MuSV) or obtained from human leukemic patients. The advantage of microscopic FTIR spectroscopy over conventional FTIR spectroscopy is that it facilitates inspection of restricted regions of cell culture or the tissue. Our results showed significant and consistent differences between the various tested normal cells (primary cells and cell lines obtained from different origins) and malignant cells either transformed by MuSV or obtained from human leukemic patients. A considerable decrease in carbohydrates and phosphates levels was seen in malignant cells compared to the normal cells. In addition, the peak attributed to the PO − symmetric stretching mode at 1082 cm −1 in normal cells was shifted significantly to 1087 in malignant cells. Furthermore, treatment of the leukemic patients with appropriate chemotherapy could be detected easily by FTIR spectroscopy; the spectral absorbance of the cells from the treated leukemic patients became very similar to normal lymphocytes. These results in addition to further differences in the shapes of various bands throughout the spectrum strongly support the possibility of developing the FTIR microscopy for the detection and study of malignant cells and probably as indication for successful treatment.