Carbenoxolone sodium (3-O-~-carboxypropionyl-ll-oxo-l8~-olean-l2-en-30-oic acid) is a drug used in the treatment of gastric ulcer. Its therapeutic use and side-effects are well documented (Baron & Sullivan, 1970), but the mode of action of the drug is at present uncertain. Lipkin (1971) demonstrated an increase in the half-life of the gastric mucosal cells and a decreased rate of DNA synthesis in mice pretreated with carbenoxolone. Goodier et al. (1 967) demonstrated an increase of acidicand neutral-staining mucosubstances in the superficial epithelium and glandular pits of the human gastric mucosa. The increase in mucus of the gastric mucosa may therefore be consequential on the gastric cell life and/or changes in the synthesis of glycoproteins. We have now investigated the effect of carbenoxolone sodium on the synthesis of gastric mucosal glycoproteins of Wistar albino rats. The rat is not the ideal experimental animal for this study, since after oral administration carbenoxolone is 60-75 % hydrolysed to enoxolone by microflora present in the rat stomach (lveson et al., 1971). However, because Dean (1968) has demonstrated a protective effect of carbenoxolone against drug-induced lesions of the stomach of rat, this species has been used in our initial investigations. Rats (Wistar albino; body wt. 2008) were housed in groups of four and allowed access to food (Spiller’s small-animal diet) and water ad lib. They were dosed orally for 7 days with carbenoxolone sodium (25mg/kg body wt.) in aqueous solution, the controls receiving saline (0.1 5 M-NaCI). The animals were then killed by cervical dislocation, and the stomachs were removed, opened and washed with ice-cold saline. The mucosa was separated from the stomach wall by scraping with a glass slide, then suspended in O.l~-phosphate buffer, pH7.4, in 1.15% (w/v) KCI (2ml) and homogenized. The UDP-glucuronyltransferase activity of this homogenate was determined by the spectrophotometric method of Dutton & Storey (1962) with o-aminophenol as