To elucidate the nature of myospherulosis, the authors tried to produce this state in vitro by mixing vitamin E, oleic acid, linoleic acid, and lanolin with human blood components, such as whole blood, washed erythrocytes, plasma, and fixed erythrocytes, respectively. Myospherulosis was produced in all mixtures in these experiments. The authors concluded the following. A thin parent body wall of myospherulosis is formed initially as a result of the physical emulsion phenomenon between lipid-containing materials and blood. Erythrocytes then are enclosed in the parent body. The parent body membrane gradually is reinforced by the deposition of plasma proteins, which are insoluble in ethanol. Thereafter, the erythrocytes become endobodies by the deposition of their contents to the membrane of the parent body. The pores of the endobodies are formed in the process of erythrocyte degeneration. The contents of the erythrocytes, such as hemoglobin, would attach to the parent body. Thus myospherulosis would become complete. In humans, the characteristics of the parent body membranes differ from each other, depending on how much the hemoglobin or a part of the endobody membrane attaches to the parent body membrane.