Floroquinolones are derivatives of nalidixic acid that act as a large-spectrum antibiotics. Adverse effects and interactions of the particular fluoroquinolone depend on its chemical structure and, often, on predisposing factors in patients, including the age, hidden or previous neurological diseases, metabolic disturbances, and allergies. The adverse effects do not significantly differ among different fluoroquinolones. They can be considered as mild, moderate and severe, and their incidence is irrespective of the gender. They can occur even after the short-term administration of these antibiotics, and usually vanish after diminishing the dose or cessation of the therapy in 24–48 hours. The adverse effects can affect nervous, digestive, urinary, cutaneous, musculo-skeletal, cardiovascular, and immune system. Rarely, fluoroquinolones can harm the spermatogenesis. Their use is not advised during pregnancy due to their possible teratogenic effects. Fluoroquinolones can interact with a variety of drugs: antacides, non-steroid antirheumatics, xantines, warfarin, and others. These drug combinations often occur during the therapeutic process in the clinical practice. The incidence of adverse effects and interactions of fluoroquinolones are low; however they can result in serious complications. The post-marketing control of these antibacterial drugs is therefore highly recommended.