Background: Coronavirus disease 2019 (COVID-19) can have a wide clinical spectrum. Objectives: The current study aimed to analyze the clinical and laboratory risk factors of the severe course of disease in patients with COVID-19. Methods: Consecutive patients with a diagnosis of COVID-19 pneumonia were included in the present study. The demographic characteristics, comorbid diseases, symptoms, chest computed tomography (CT) findings, laboratory data, oxygen saturation (SpO(2)), and body temperature of the patients were recorded. The coexistence of pulmonary infiltration in CT and SpO(2) of <= %93 on fingertip pulse oximeter was defined as the severe course of the disease. Results: A total of 475 patients were included in the current study. The mean age of the patients was 52.02 +/- 15.9 years, and 259 (54.5%) participants were male. The disease was mild and severe in 80% (n=380) and 20% (n=95) of the study subjects, respectively. The age of > 50 years, coexistence of hypertension (HT) and diabetes mellitus (DM), neutrophil-to-lymphocyte ratio (NLR) of > 4, lactate dehydrogenase (LDH) of > 240 U/L, C-reactive protein (CRP) of > 8 mg/dL, and D-dimer of >= 1000 ng/mL were determined to be the risk factors for the severe course of the disease. Conclusion: Age, NLR, CRP, LDH, D-dimer, comorbidity, and coexistence of DM and HT were the independent risk factors for the severe course of the disease. The aforementioned factors should be taken into account during risk stratification and management of patients with COVID-19.