This is an academic doctor's thesis in Danish with summaries in German and English. The earlier literature on problems of pleurisy is reviewed and a detailed account is given of some 986 hospital cases of apparently primary exudative pleuritis and of the results of the follow-up and reexamination of the surviving patients some six years after the primary attack. A good general picture of the disease is given as it occurs in the population of Copenhagen, with special emphasis on the prognosis. In 309 cases the pleuritis was unquestionably tuberculous and most of the remaining save 14 also seemed to be tuberculous. The thesis embodies the outcome of thorough, well planned work for several years and is a valuable contribution to the clinical study of primary exudative pleuritis.