Objectives. The aim of the study was to analyze predictive factors of bacteraemia in patients seen in the emergency department (ED) for an episode of infectious disease. Patients and methods. Observational, retrospective and descriptive analytical study of all blood cultures extracted in an ED in adult patients (≥ 18 years) seen in ED due to infectious disease from 1-1-2019 to 1-7-2019. The follow-up was carried out during 30 days. Thirty-eight variables for predicting bacteraemia were assessed. They covered epidemiological, comorbidity, functional, clinical and analytical factors. Univariate and multivariate logistic regression analysis was performed. Results. A total of 1,425 blood cultures were finally enrolled in the study. Of those were considered true bacteremia 179 (12.6 %) and as negative blood cultures 1,246 (87.4 %). Amongst negatives, 1,130 (79.3%) without growth and 116 (8.1%) as contaminants blood cultures. Five variables were significantly associated with true bacteraemia: serum procalcitonin (PCT)