Inflammatory bowel diseases involve chronic inflammation of all digestive tract or only part of it, which mostly includes Crohn’s disease and ulcerative colitis. The most common symptoms are diarrhea, pain and cramps in the abdomen, weight loss, blood in the stool and decreased appetite. They can also cause anemia due to bloody diarrhea. Men and women are at equal risk of getting the disease. The diagnosis is most often made between the ages of 15 and 40. The aim of medical treatment is to reduce the inflammation that activates the signs and symptoms of the disease, and the drugs used are mainly aimed at non-specific suppression of the immune system. One of the therapies in the treatment of inflammatory bowel disease is biological therapy. Biological drugs are defined as drugs with one or more active substances that are derived or synthesized from biological materials. They are produced by the recombinant DNA method in such a way that the genes required for the synthesis of a particular protein are incorporated into the stem cell genome by a vector, after which the protein is synthesized and isolated from the cell and can be used as an active substance. They are divided into anti-TNF-alpha, anti-integrin, anti-IL-12/23 drugs and JAK inhibitors. Anti-TNF-α drugs are the most commonly used and include TNF-α receptor blockers and soluble TNF-α receptors. The aim of this paper is to present the efficacy and safety of biological therapy in patients with inflammatory bowel disease in a way that for each of the diseases will be explained therapy and course of treatment. The paper will present the application of biological therapy in the Zadar General Hospital in patients with Crohn's disease and ulcerative colitis, depending on gender, age and medications they take.