There is considerable biologic and physiologic heterogeneity among patients who meet standard clinical criteria for acute respiratory distress syndrome (ARDS). In this study, we tested the hypothesis that there exists a sub-group of ARDS patients who exhibit a metabolically distinct profile. We examined undiluted pulmonary edema fluid obtained at the time of endotracheal intubation from 16 clinically phenotyped ARDS patients and 13 control patients with hydrostatic pulmonary edema. Non-targeted metabolic profiling was carried out on the undiluted edema fluid. Univariate and multivariate statistical analyses including principal components analysis (PCA) and partial least squares discriminant analysis (PLSDA) were conducted to find discriminant metabolites. 760 unique metabolites were identified in the pulmonary edema fluid of these 29 patients. We found that a subset of ARDS patients (6/16, 38%) presented a distinct metabolic profile with the overrepresentation of 235 metabolites compared to edema fluid from the other 10 ARDS patients, whose edema fluid metabolic profile was indistinguishable from those of the 13 control patients with hydrostatic edema. This "high metabolite" endotype was characterized by higher concentrations of metabolites belonging to all of the main metabolic classes including lipids, amino acids, and carbohydrates. This distinct group with high metabolite levels in the edema fluid was also associated with a higher mortality rate. Thus, metabolic profiling of the edema fluid of ARDS patients supports the hypothesis that there is considerable biologic heterogeneity among ARDS patients who meet standard clinical and physiologic criteria for ARDS.