Gelatinases A and B are matrix metalloproteinases secreted as inactive pro forms and are capable of degrading basement membrane components after activation in the extracellular environment. To determine whether the presence of gelatinases A (noninflammatory cells) and B (inflammatory cells) in epithelial lining fluid (ELF) is associated with the adult respiratory distress syndrome (ARDS), we studied 28 patients divided into four groups based on the presence of ARDS and/or multiple organ failure (MOF). Gelatinase activities were quantified in ELF using zymography. ARDS patients had larger ELF volumes than non-ARDS patients: 9.2 +/- 8.5 ml/100 ml recovered lavage fluid (n = 18) vs. 1.9 +/- 1.7 ml/100 ml (n = 11), respectively (P < 0.001). The presence of activated gelatinase A in ELF was a sensitive (16 out of 18 ARDS patients, 89%) and specific (0 out of 11 non-ARDS patients with or without MOF) marker for ARDS. Activated gelatinase (A + B) activities per microliter ELF were correlated with albumin concentrations in ELF (P < 0.01), and activated gelatinase activities in ELF were correlated with the volume of ELF (P < 0.0005). This could suggest an involvement of these gelatinases in alveolar-capillary permeability increase.