Background: Interleukin-6 is a multifunctional cytokine with well-defined pro- and anti-inflammatory properties. Binding to the receptor complex composed of specific interleukin-6-receptor (IL-6R) and transmembrane glycoprotein gp130, it stimulates various signalling cascades. Intracellular signal transduction involves both STAT-dependent, and STAT-independent mechanisms. IL-6R exists in the soluble and the membrane-bound forms, thus were described the classical signalling and the trans-signalling pathways. The pro-inflammatory response occurs via trans-signalling, while the anti-inflammatory effects are mediated by classical signalling pathway. IL-6 is produced by cardiovascular components. The high levels of IL-6 are identified in the inflammatory diseases. Conclusions: IL-6 expresses the well-defined pro- and anti-inflammatory properties. The experimental studies have revealed classic signalling pathway with regenerative and anti-inflammatory effects (via the membrane-bound IL-6R), and trans-signalling responsible for the pro-inflammatory response (via the soluble form sIL-6R). The intracellular signal transduction involves the activation of STATs, MAPK, and PI3K cascades. It has been proved that in the cardiovascular pathologies the serum levels of IL-6 correlate with the disease severity and the degree of myocardial damage, being the indicator of heart disease and a predictive factor of adverse outcomes.