The acute respiratory distress syndrome (ARDS) is an important cause of acute respiratory failure with a high mortality rate. The mechanism of resolution of the late organizing phase remains uncertain. The ACE gene contains a polymorphism based on the presence (insertion, I) or absence (deletion, D) within an intron of a 287-bp nonsense DNA domain, resulting in three genotypes (DD and II homozygotes, and ID heterozygotes). It has been shown that I/D polymorphism of ACE gene may account for half the variance of serum ACE levels in the Caucasians. Polymorphism of the ACE gene has also been shown to contribute to the development of some respiratory diseases. We hypothesize that the presence of ACE gene polymorphism can affect the outcome of ARDS. The objective of this proposed study is to determine the genotypes of ACE gene polymorphism and assess the influence of ACE genotype on the outcome and pulmonary resolution of patients with ARDS. Patients diagnosed to have ARDS are eligible for possible inclusion into the study. The ACE genotype of all patients with ARDS will be determined by polymerase chain reaction (PCR) amplification of the respective fragment for the D and I alleles from intron 16 of the ACE gene and size fractionation by electrophoresis. The outcome of patients with ARDS in the three genotypes will be compared.