This review is based on the contents of an international congress entitled, “Surfactant 2004”, organized by Drs. B. Lachmann and L.M.G. van Golde and held in Berlin, Germany. This is the fourth meeting of its kind; the first one was held in 1989. The purpose was to bring together investigators, interested in surfactant research from different disciplines to review progress in basic and clinical sciences, evaluate findings from clinical trials, and build upon the current knowledge to design better clinical trials for the prematurely born infant and other groups of patients, who are identified with surfactant dysfunction, as well as formulate new hypotheses for surfactant investigation both at the basic science and clinical science levels. Although the importance of surfactant in normal lung function was initially appreciated in the case of the prematurely born infant the importance of surfactant throughout life and the roles, especially of the surfactant proteins, not only in surfactant-related activities but also in the innate host defense of the lung has led to a tremendous increase in research activity in the field. The work presented in this meeting is summarized under four general topics: biophysical, innate host defense, surfactant proteins and pulmonary disease, and clinical studies of surfactant.