BACKGROUND/AIMS Humic acid (HA) formed by the decomposition of organic matter is a high-molecular-weight polymer. Humic-derived substances are potential drugs for human health, and their role in the prevention and treatment of diseases, like diabetes, antiviral, UV-B protective effect, cancer, and cardiovascular disease, is emphasized in various studies. It has antiulcerogenic, antitumor. Yang et al. demonstrated that HA exerts an antiproliferative effect and growth inhibition on HL-60 cells through the induction of apoptosis. A study showed that the antiulcer effect of Shilajit (HAs extracted from Shilajit) samples may be due to antimicrobial, anti-inflammatory, antianxiety, antioxidant, healing, and regenerative effects. The present study aimed to investigate the effects of HA on cultures of the chronic myeloid leukemia cell line in vitro. MATERIAL and METHODS We determined the apoptotic effect of HA in K562 cells by using various molecular methods. For cell viability, HA was tested in vitro against K562 cell lines using the MTT colorimetric process. Bax, bcl-2, casp-3, and casp-9 expressions were quantified by Western blot. Apoptosis analysis has been made with the Annexin-V/PI method. RESULTS The IC50 values of HA were determined 100 mg mL 1 for the K562 cell line. HA has been shown to inhibit cell proliferation. As the bcl-2/ bax ratio decreased and increasing the levels of caspase-3 and caspase-9, the cells underwent apoptosis. CONCLUSION As a result, HA showed the anticancer effect on leukemia cells. In the future, HA can be used as a chemopreventive agent in leukemia treatments.