Acute effects of CHBrCl2 on microsomal lipid metabolism were studied in the liver of male Wistar rats administered a single oral dose (215 mg/kg). 3 h after administration, the modulation of phospholipid metabolism and the accumulation of triacylglycerol (TG) were noted in the microsomal membranes. A marked decrease in the synthetic rate of phospatidylcholine (PC) could be explained by a fall in the microsomal activity of CTP:phosphocholine cytidylyltransferase. A decrease in glycerophosphate acyltransferase activity and an enhancement in phosphatidate phosphatase activity seemed to offset each other, and consequently no significant change was observed in the synthetic rate of microsomal TG. These alterations in microsomal lipid metabolism can be regarded as one of the manifestations of hepatotoxicity of CHBrCl2.