In December 2019, a novel illness called coronavirus disease 2019 (COVID 19) was described in China and became pandemic in a few months. The first case was detected in Argentina on March 3, 2020. A multicentre prospective observational cohort study on hospitalized patients with COVID 19 was conducted in 4 hospitals in San Isidro district from March 1, 2020 to October 31. Data was obtained by the attendant physician. 668 patients were included, the median age was 54 years, and 42.7% were female. Male sex and older age were associated with COVID 19 disease and more strongly with severity. Most frequent symptoms were fever and cough followed by dyspnoea, myalgia, odynophagia, headache, anosmia, and diarrhoea. Nonsevere patients had more upper respiratory symptoms while severe patients had mainly lower respiratory symptoms on admission. Most common comorbidities were arterial hypertension, diabetes, and cardiovascular disease. A great proportion of patients had normal thorax X ray and ground-glass opacity in tomography. In severe patients, radiography and tomography had a predominant ground glass pattern, but normal radiography and tomography on presentation were present in 22% and 5.9%, respectively. The absence of fever and normal radiology on admission neither excluded the disease nor further severity. PCR elevation was related with COVID 19 disease and with severity, while lymphopenia was more related with the disease and leukocytosis and thrombocytopenia with severity. 8, 4% of patients were health care workers. The mortality rate was 12.4%, 32.7% in severe patients and 61.2% in ventilated patients. Mortality was higher in the public hospital, probably associated with patients with older age and more comorbidities. All these observations can contribute to the knowledge of this disease in terms of diagnosis and prognosis.