This brief paper presents the vapoure pressure data of the following fluids used in vacuum pumps : DC 704, DC 705, Apiezon B, Apiezon C, Lion A, Di - 2 -ethylhexyl phthalate (DEHP), Di-2-ethyl- hexyl sebacate (DEHS), Cellulube 220, Cellulube 300, Convalex 10, and OS 124. Measurements have been made in the pressure range of 0. 5 to 20 Torr with the oil-manometer in which the samples themselves are used. It has been previously reported for this method to be most suitable in the case of measuring the vapour pressures of the vacuum pump oils near at a boiler temperature (J. Vac. Soc. Japan 1 222 (1958)). In discussion, the data obtained in study have been compared with those by other investigators. Consequently, it is proved that, this for each sample, all these data measured in the different range of pressure can be suffici-ently plotted on a line expressed by the equation, log P= a-b/T c log T.