A cross-sectional study.The aim of this study is to describe the profile of patients with acute low back pain (LBP) who sought emergency departments (EDs) in Brazilian public hospitals. We also described the profile of these patients according to the STarT Back Screening Tool (SBST).LBP is the most common musculoskeletal condition worldwide and is one of the main complaints in EDs. There is a lack of evidence describing the profile of these patients from low- to middle-income countries.This is a cross-sectional study involving patients with a new episode of nonspecific acute LBP that was conducted between August 2014 and August 2016. Variables related to clinical, psychological, sociodemographic and work status characteristics were investigated through structured, in-person oral questionnaire.A total of 600 patients were included in the study. The majority of the patients were women (58%), with a median of eight points on pain intensity (measured on an 11-point scale) and 17 points on disability (measured on a 24-item questionnaire). With regards to the SBST evaluation, 295 (49.2%) patients were classified as being at high risk of developing an unfavorable prognosis with a median pain intensity of nine points on pain intensity, 20 points on disability, and seven points on depression (measured on an 11-point scale). Despite this, the majority of the patients (74%) continued working normally without interference from LBP.Identifying the profile of patients seeking care in EDs can help to define effective management for LBP in low- and middle-income countries. Patients with nonspecific acute LBP who seek EDs in Brazil present high levels of pain intensity and disability. Most patients were classified as having a high risk of developing an unfavorable prognosis.2.