The paper describes the catalytic activity of butyrylcholinesterase (BuChE) measured in plasma, liver, white adipose tissue, heart, and brain of rats intraperitoneally administered a single non-lethal dose of cycloheximide (2.0 mg/kg body weight; CHM). The BuChE assay was performed on rats of both sexes either administered CHM or saline (controls), and killed 2, 3, 4, 5, 10 days later. A significant decrease of BuChE catalytic activity was observed in all tested tissues except plasma. In animals of both sexes, the lowest BuChE catalytic activity was found in the liver (2-6%), while it was higher in white adipose tissue, heart, and brain. However, the respective values remained significantly different from controls (33-67%, 49-62%, and 14-71% in males, and 24-82%, 72-86%, and 33-67% in females). Since there was no effect of CHM on BuChE catalytic activity in plasma, the data suggest that CHM inhibits the synthesis of BuChE rather than its active site.