Tumor lysis syndrome (TLS) occurs as a result of massive lysis of malignant cells and release of intracellular contents into the systemic circulation. It can lead to hyperuricaemia, hyperkalaemia, hyperphosphataemia and hypocalcaemia. TLS is most commonly present after initiation of anticancer therapy but it can also develop spontaneously (STLS--spontaneous tumor lysis syndrome). In the article, pathophysiology, classification, risk factors and recommendations of management in TLS, with a special focus on solid tumors, are discussed. The keys to the identification of high-risk patients, prevention and management of TLS are included in presented guidelines.