Background/Aim. Coronavirus disease 2019 (COVID-19) is a predominantly respiratory disease caused by severe acute res-piratory syndrome coronavirus 2 (SARS-CoV-2). The aim of this study was to determine whether there were parameters that could predict the development of a severe clinical picture and fatal outcomes in COVID-19 patients. Methods. The study involved 632 patients treated at the Clinic for Infectious Diseases, University Clinical Center Kragujevac, from June 2020 to February 2021. All patients were divided into two groups according to the need for oxygen therapy (Sat 0₂ < 94 %). Results. Our results showed that high body mass index (BMI) was singled out as a risk factor for the development of a severe clinical picture (BMI, OR_adjusted = 1.263; 95% CI = 1.117 – 1.427; p < 0.001). Prothrombin time (OR_adjusted = 1.170; 95% CI = 1.004 - 1.364; p = 0.045), as well as low al-bumin values (OR_adjusted = 0.878; 95% CI = 0.804 - 0.958; p = 0.003), had a predictive significance for the development of a severe clinical picture. Factors that were of predictive im-portance in patients with fatal outcomes were C-reactive protein (CRP) (OR_adjusted = 1.010; 95% CI = 1.001 – 1.019; p = 0.031), lactate dehydrogenase (LDH) (OR_adjusted = 1.004; 95% CI = 1.001 – 1.006; p = 0.002), and X-ray of the lungs (OR_adjusted = 1.394; 95% CI = 1.170 – 1.661; p < 0.001). Conclu-sion. The study showed that routine, clinical laboratory pa-rameters can be important in the early detection of patients with a potentially severe clinical picture and fatal outcomes. In patients with a mild clinical picture, CRP, LDH, ferritin, and serum albumin levels may timely indicate disease progression. Monitoring these parameters is of essential importance for the timely clinical assessment of patients with COVID-19 and, thus, the prompt application of adequate therapeutic proto-cols in the treatment of these patients.