Technological advances in modern medicine have led to the development of biological therapy, which includes drugs manufactured in biological sources and involves recombinant peptides and proteins, monoclonal antibodies, immunoconjugates, cell therapy and nucleic acid therapy. In addition to the original biological drugs, biosimilar drugs and biobetters are also being produced today. The use of biopharmaceuticals may lead to side effects due to excessive immune system activation, active substance immunogenicity, the occurrence of immunosuppression, autoimmunity and atopy in the organism, cross-reactivity with other molecules, and other mechanisms. To date, biologics have improved the treatment of many diseases, such as rheumatic diseases, inflammatory bowel disease, tumors, diabetes and others. Although conventional therapy is the basis for inflammatory bowel disease treatment today, biological therapy has allowed changes in the course of the disease, long-term maintenance of remission and reduction of complications in patients. The introduction of biologics in the treatment of malignant diseases has improved patient survival and life quality. Biological drugs have also shown significant efficacy in the treatment of rheumatic diseases, reducing the onset of permanent complications and improving the outcome in most patients. Biological therapy disadvantages are the need for parenteral administration and high price, but due to their many benefits, their use in contemporary clinical practice is increasing. Biologics are increasingly taking over the pharmaceutical market. Furthermore, many new biological drugs are in the process of development and clinical research and will surely improve the treatment of many more medical conditions.