In the observation on the tissue culture of 3 adults pleural effusion which has no pathologic condition, the following results were obtained. (1) The cell component of these human pleural effusion closely relative of non-pathologic human ascites, of pleural and peritoneal fluid of animals. (2) Phagocytes in the pleural effusion seem to be same cytological natures with human ascites, also it resembles quite closely to that of blood monocyte. (3) Phagocytes occupy 89.3% of the total, and the majority of them are the small size phagocytes. (4) The average cell count is 1626/m㎥.