Interleukin‑6 (IL‑6) is proinflammatory cytokine that produces multifunctional efects. It is also involved in the regulation of immune reactions, hematopoiesis and inflammatory state. Interleukin‑6 has been shown to be associated with tumor progression including inhibition of cancer cells apoptosis and stimulation of angiogenesis. Anti‑IL‑6 therapy is a new strategy in the inflammatory autoimmune diseases and cancer. Clinical studies have shown elevated serum IL‑6 concentrations in patients with endometrial cancer, non‑small cell lung carcinoma, colorectal cancer, renal cell carcinoma, breast and ovarian cancer. Serum IL‑6 levels correlate with tumor stage, and survival of patients. In this article we have focused on a role of IL‑6 as a prognostic factor in several malignancies such as colorectal cancer, breast cancer, gastric cancer and pancreatic cancer.