For a long time markers that can detect a malignant cell transformation as ear ly as possible have been sought. Substances which have been discovered are known as tumor markers. Stem cell factor (SCF) and interleukin 3 (IL-3) are members of a group of glycoprotein growth factors called hematopoietic cytokines (HCs). These factors take part in the regulation of developmental processes of hematopo ietic progenitor cells and it was proved that HCs can be produced by different c ancer cells, including colorectal cancer. The aim of this study was to investiga te a potential role for SCF and IL-3 as tumor markers for colorectal cancer. We compared the serum levels of SCF and IL-3 in colorectal cancer patients with t hose in healthy subjects (control group) and commonly accepted tumor markers, su ch as carcinoembryonic antigen (CEA) and carbohydrate antigen 19-9 (CA 19-9). We defined the diagnostic sensitivity, specificity, positive predictive value, n egative predictive value, and receiver-operating characteristics (ROC) curve of tested substances. SCF and IL-3 were determined using enzyme-linked immunosor bent assay (ELISA). CEA and CA 19-9 were measured by microparticle enzyme immun oassay. The serum levels of HCs and tumor markers were investigated in 75 patien ts with colorectal cancer and in 40 healthy subjects. There were significant differences in the level of circulating SCF and IL-3 in the color ectal cancer patients compared to the control group. Moreover, the diagnostic se nsitivity of SCF was higher than the sensitivity of CEA and CA 19-9. The SCF ar ea under the ROC curve was larger than the IL-3 area but smaller than the CEA a nd CA 19-9 areas. The diagnostic specificities of cytokines were lower than tho se of tumor markers, but the combined use of cytokines and tumor markers increas ed the diagnostic values. The highest values of diagnostic parameters were obser ved for the combined use of SCF and CA 19-9. These results suggest a potential role for SCF and IL-3 as tumor markers for colorectal cancer, especially in com bination with CEA or CA 19-9. For a long time markers that can detect a malignant cell transformation as ear ly as possible have been sought. Substances which have been discovered are known as tumor markers. Stem cell factor (SCF) and interleukin 3 (IL-3) are members of a group of glycoprotein growth factors called hematopoietic cytokines (HCs). These factors take part in the regulation of developmental processes of hematopo ietic progenitor cells and it was verified that HCs can be produced by different c cells, including colorectal cancer. The aim of this study was to investiga te a potential role for SCF and IL-3 as tumor markers for colorectal cancer. We compared the serum levels of SCF and IL-3 in colorectal cancer patients with t hose in healthy subjects (control group) and frequently accepted tumor markers, su ch as carcinoembryonic antigen (CEA) and carbohydrate antigen 19-9 (CA 19-9). We defined the diagnostic sensitivity, specificity, positive predictive value, n egative predictive value, and receiver-o SCF and IL-3 were determined using enzyme-linked immunosorbent assay (ELISA). CEA and CA 19-9 were measured by microparticle enzyme immun oassay. The serum levels of HCs and tumor markers were investigated in 75 patien ts with colorectal cancer and in 40 healthy subjects. There were significant differences in the level of circulating SCF and IL-3 in the color ectal cancer patients compared to the control group. higher than the sensitivity of CEA and CA 19-9. The SCF ar ea under the ROC curve was larger than the IL-3 area but smaller than the CEA a nd CA 19-9 areas. The diagnostic specificities of cytokines were lower than tho se of tumor markers, but the combined use of cytokines and tumor markers increas ed the diagnostic values. The highest values ​​of diagnostic parameters were observed ved for the combined use of SCF and CA 19-9. These results suggest a potential role for SCF andIL-3 as tumor markers for colorectal cancer, especially in com bination with CEA or CA 19-9.