The concentration of plasma free fatty acids in rats was significantly increased after a short period of exposure to inhalation of carbon disulphide (4 h, 2 mg/1). In contrast, after a longer period of exposure (15 h overnight, 2 mg/1) the concentration of plasma free fatty acid was significantly decreased despite a small hypoglycaemia. At the same time plasma urea concentration was significantly higher in CS2-treated rats. The total esterified fatty acid content of plasma was lower after exposure, but there was no change in plasma glycerol. Following an intragastric water load, no differences were observed in urine flow rate nor in renal clearances of urea and inulin between control and treated rats. It is concluded that the rate of urea production is significantly increased during acute CS2-intoxication, and it is suggested that two factors contribute to this effect: first, an increased breakdown of proteins with which CS2 or its metabolic products have reacted; and secondly an increased rate of utilization of plasma glucose associated with increased gluconeogenesis from amino acid precursors. It is further suggested that the stress effects of CS2 dominate in the short term before being overcome by a diminished sympathetic response. When rats were exposed to CS2 overnight without free access to water, the great vessel haematocrit was significantly lower than in corresponding controls. This was shown to be accounted for by differences in plasma volume. No such difference was observed when rats had free access to water during exposure. These effects probably reflect differing rates of water loss under mildly dehydrating conditions, but a direct effect of CS2 on the cardiovascular system is not excluded.