Bacterial infections are infectious diseases caused by the action of pathogenic bacteria present in sufficient numbers to overcome the defense mechanisms of the host. Although a large number of antibiotics have been developed to treat bacterial infections, more and more bacteria are resistant to antibiotics, which requires the development of new methods and principles for their treatment. The choice of therapy depends on the bacterial pathogen and the characteristics of the patient. The purpose of this thesis is to analyze the reports of suspected adverse reactions to antibacterials for systemic use (ATC J01) reported to the Agency for Medicinal Products and Medical Devices of Croatia (HALMED) in the period from October 1, 2003 to December 31, 2021. 4544 reports were received and analyzed by years of receipt, age and gender of a patient, reporter, seriousness, seriousness criteria, mortality, distribution to System Organ Class (SOC) of the Medical Dictionary for Regulatory Affairs (MedDRA) and J01 active substances, which most commonly caused adverse reactions, and active substances that were most commonly reported with the active substances of ATC J01 medicines group. In the total number of all reports of suspected adverse reactions to medicinal products in the period from 2003 to 2021, 8.5% were suspected adverse reactions reports for J01 medicines group. The highest number of reports was recorded for female patients (64.2%) and the age group from 18 to 44 years (29.7%). Most cases were reported by physicians (45.3%). The largest number of reported cases was not serious (67.1%). The largest number of adverse reactions belongs to SOC Skin and subcutaneous tissue disorders (37.5%) and SOC Digestive system disorders (37.3%), and the most common adverse reactions were diarrhea, pruritus/itching, rash and nausea. The active substances that most commonly caused adverse reactions were: a combination of amoxicillin trihydrate and potassium clavulanate (18.7%), azithromycin (6.3%) and clarithromycin (5.7%). Active substances from other ATC medicines groups that were most commonly reported with active substances from J01 medicines group and that were suspected, interacting or concomitant with J01 medicinal products were pantoprazole and bisoprolol. The analyzed data from the national database of adverse reactions were compared with the data from the European and global database of adverse reactions to medicinal products and the consistency of the data was observed. HALMED's goal is to improve and facilitate the reporting of suspected adverse reactions to medicinal products and to raise the awareness of healthcare professionals and patients about the importance of the same.