Before the toxic symptoms elicited by a solvent vapor can be diagnosed and treated intelligently, it is helpful to know certain physiologic reactions of the compound. They are (1) the rate and extent of absorption into the individual's body, (2) the rate of excretion, (3) the rate and the amount of the compound metabolized by the body, (4) the site of action of the vapor and (5) in what manner the toxic action is elicited. In this paper we have attempted to give a partial answer to these questions as they apply to carbon disulfide (CS2). The absorption of any solvent vapor into the blood stream takes place primarily by way of the alveoli. The amount of vapor absorbed is regulated mainly by the vapor concentration breathed, the length of exposure and the coefficient of distribution1 of the solvent between air and blood and between blood and tissues. This